Coast to Cactus Weather Examiner

National Weather Service - S a n D i e g o

Volume 28 Number 3 weather.gov/sandiego July 2021

The New Normal adapted from climate.gov Inside this issue: Climate normals are 30-year averages of key climate observations made at weather stations and corrected for bad or missing val- The New Normal 1 ues and station changes over time. From the daily weather report to seasonal forecasts, the Normals are the basis for judging how temperature, rainfall, and other climate conditions compare to what’s The New Normal—SoCal 4 normal for a given location in today’s climate. For the past decade, the Normals have been based on weather observations from 1981 to 2010. In early May, climate experts at Aviation forecasting and 7 NOAA’s National Centers for Environmental Information (NCEI) re- support at nws san diego leased an updated collection—hourly, daily, monthly, and annual Normals for thousands of U.S. locations, states, regions—based on the Wildland Fire Support 10 weather experienced from 1991 to 2020.

A warmer normal Spring-Summer Outlook 10 The U.S. Climate Normals collection has 10 versions: 1901- 1930, 1911-1940, and so on through 1991-2020. In the image below, we’ve compared the U.S. annual average temperature during each Quarterly Summary 11 Normals period to the 20th-century average (1901-2000). Places

Annual U.S. temperature compared to the 20th-century average for each U.S. Climate Normals period from 1901-1930 (upper left) to 1991-2020 (lower right). Maps by NOAA Climate.gov, based on analysis by Jared Rennie, North Carolina Institute for Climate Studies/NCEI. The New Normal—continued where the annual temperature during a given Normals era was colder than the 20th-century average are blue; places where the temperature was warmer than average are red. The influence of long-term global warming is obvious: the earliest map in the series has the most widespread and darkest blues, and the most recent map has the most widespread and darkest reds. Today, the normal annual temperatures across the country are warmer than the 20th- century average virtually everywhere. From 1901-1930, the annual average temperature was mostly colder than the 20th-century average. What’s also obvious in these comparisons is that the influence of global warming on normal U.S. temperature isn’t the same everywhere or during every 30-year period on record. Otherwise, the maps would have transitioned gradually from dark blue everywhere to dark red everywhere. In fact, a few locations do exhibit that pattern of gradual, steady warming from one Normals era to the next. Southeastern Oregon. Southern Florida. You can probably spot others. But in many places, the pace of warming changes from decade to decade due to other climate influences, both natural and human (think the Dust Bowl and smokestack pollution before the Clean Air Act). For example, in much of the U.S. Gulf Coast region, the maps show that normal annual temperatures were actual- ly warmer than the 20th-century average in the first four sets of Normals. Beginning with the 1941- 70 Normals, they reverted, with normal annual temperature growing increasingly cooler over the next two periods. That cooling pattern began to weaken with the 1971-2000 Normals, and it has all but disappeared today. Annual mean temperature change from the old 1981-2010 normals to the new 1991-2020 normals. Map CISESS/NCEI.

A wetter or drier normal? “It varies” is the main message of the maps showing how the normal annual precipitation across the country has changed. Precipitation—regardless of human-caused climate change—varies a lot from place to place across the United States. Few places exhibit a precipitation trend that is either steadily wetter or steadily drier than the 20th-century average. Instead, drier areas and wetter areas shift back and forth without an obvious pattern. For example, the Southwest was much wetter than the 20th-century average in the 1901-30 and 1911-40 Normals, and then mostly drier than the 20th-century average in the next four Nor- mals. The 1961-90 Normals were a mix, with few areas either very wet or dry relative to the 20th- century average. The next two Normals periods—1971-2000 and 1981-2010— were once again much wetter than the 20th-century average across much of the Southwest, but the pattern has reversed in the new Normals. That inconsistency isn’t surprising, despite the fact that human-caused climate change The New Normal—continued

Normal annual U.S. precipitation as a percent of the 20th-century average for each U.S. Climate Normals period from 1901-1930 (upper left) to 1991-2020 (lower right). Maps by NOAA Climate.gov, based on analysis by Jared Rennie, North Carolina Institute for Climate Studies/NCEI. likely is influencing U.S. precipitation in some places and seasons. It’s just that what controls precipitation varies so much from place to place and month to month that the influence of global warming also varies a lot. Some parts of the country are projected to see increases in annual average precipitation, and others may see decreases. Some may see wetter winters but drier summers, with little net change in annual average precipitation—but big impacts on natural ecosys- tems and agriculture that depend on a certain seasonal cycle. Some will see a shift in the type or intensity of precipitation without seeing a change in their annual total. More rain, less snow. More downpours, with longer dry spells between. With all this nuance, it’s not surprising that precipitation maps don’t show the same unmis- takable fingerprint of climate change that the temperature maps do. And yet, it’s probably not a coincidence that the last four maps in the series—the 1961- 1990, 1971-2000, 1981-2010, and 1991-2020 Normals—are nationally the four wettest-looking maps in the collection. At least some of that wetness relative to the 20th- century average is linked to the overall warming and “wetting” of the atmosphere that’s occurred as rising temperatures enhance Annual mean precipitation change from the old 1981-2010 normals evaporation of water from the to the new 1991-2020 normals. Map CISESS/NCEI. ocean and land surface. The New Normal—continued What used to be normal The 1991-2020 Normals tell us what is normal in today’s climate. NOAA does other analyses that tell us about what used to be normal. For its monthly and annual climate monitoring, temperature averages and precipitation totals are ranked since 1895, with many states ranking towards warm extremes recently. Also, U.S. and global climate conditions are compared to the 20th -century average.

Average annual temperatures for the contiguous United States from 1895 to 2020 (orange line), along with the warming trend of 0.16˚Fahrenheit per decade (red line). Graph by NOAA Climate.gov, based on data from NCEI Climate at a Glance.

Having the entire 20th century included for comparison means the baseline captures more of the range of natural variability that’s possible in U.S. and global climate. It also provides a rea- sonable—but conservative—indication of the influence of long-term warming on temperatures. The Normals are shifting, but NOAA isn’t losing track of climate change.

The New Normal—SoCal Edition by Miguel Miller

When the new normals were released in early May 2021, Southern California forecasters and climate lovers were eager to see 1) how much warmer the new normals would be compared to the previous normals, and 2) what changes to precipitation there would be. The no-brainer is that the new normals would reflect a warmer climate for all stations in Southern California. And that has been confirmed for most of the region. The new normal precipitation ended up drier than the old normals for all stations.

Temperature Monthly average temperatures in the 1991-2020 normals increased most months for San Die- go, Santa Ana, Riverside, Big Bear Lake and Indio. Surprisingly, monthly average temperatures ac- tually fell slightly in Victorville. The charts on the following page illustrate that average temperatures (average of maxi- mum and minimum temperatures of each day) for the month made a small increase near the coast (San Diego and Santa Ana) and in the valleys (Riverside). They decreased slightly in the high desert (Victorville). A very small increase was found in the low desert (Indio) and in the mountains (Big Bear Lake). The New Normal—SoCal Edition—cont’d

Santa Average Temp Average Temp Vic- Average Temp Average Temp Ana 1981-2010 1991-2020 change torville 1981-2010 1991-2020 change Jan 58.4 59.0 0.6 Jan 46.1 45.8 -0.3 Feb 59.1 59.4 0.3 Feb 49.0 48.4 -0.6 Mar 60.8 61.5 0.7 Mar 53.9 53.4 -0.5 Apr 63.3 63.7 0.4 Apr 59.4 58.6 -0.8 May 66.1 66.4 0.3 May 67.4 66.2 -1.2 Jun 69.0 69.5 0.5 Jun 74.9 74.7 -0.2 Jul 73.1 73.6 0.5 Jul 81.0 80.9 -0.1 Aug 74.3 75.0 0.7 Aug 80.5 80.1 -0.4 Sep 73.1 73.8 0.7 Sep 74.5 74.4 -0.1 Oct 68.7 69.4 0.7 Oct 63.6 63.3 -0.3 Nov 62.7 63.4 0.7 Nov 52.8 52.3 -0.5 Dec 57.7 58.2 0.5 Dec 45.2 44.7 -0.5 Annual 65.6 66.1 0.5 Annual 62.4 61.9 -0.5

River- Average Temp Average Temp Big Bear Average Temp Average Temp change change side 1981-2010 1991-2020 Lake 1981-2010 1991-2020 Jan 56.0 56.4 0.4 Jan 34.1 34.8 0.7 Feb 57.2 56.9 -0.3 Feb 34.6 34.7 0.1 Mar 59.7 59.6 -0.1 Mar 38.6 39.1 0.5 Apr 63.8 63.9 0.1 Apr 43.9 44.2 0.3 May 68.9 68.0 -0.9 May 51.9 51.5 -0.4 Jun 73.9 74.1 0.2 Jun 59.0 59.3 0.3 Jul 79.5 79.5 0.0 Jul 64.7 65.1 0.4 Aug 80.3 80.7 0.4 Aug 63.6 64.1 0.5 Sep 76.8 77.4 0.6 Sep 57.9 58.5 0.6 Oct 69.0 69.4 0.4 Oct 48.5 49.2 0.7 Nov 60.7 61.4 0.7 Nov 40.3 40.6 0.3 Dec 55.1 55.6 0.5 Dec 34.5 34.8 0.3 Annual 66.8 66.9 0.1 Annual 47.7 48.0 0.3

San Average Temp Average Temp Indio Average Temp Average Temp change Diego 1981-2010 1991-2020 change 1981-2010 1991-2020 Jan 57.1 58.4 1.3 Jan 58.3 58.6 0.3 Feb 57.9 59.0 1.1 Feb 61.6 62.2 0.6 Mar 59.4 60.7 1.3 Mar 68.1 68.5 0.4 Apr 61.7 62.9 1.2 Apr 74.1 74.5 0.4 May 64.0 64.8 0.8 May 81.7 81.2 -0.5 Jun 66.4 67.2 0.8 Jun 88.6 89.2 0.6 Jul 70.0 70.7 0.7 Jul 93.8 94.1 0.3 Aug 71.6 72.4 0.8 Aug 93.4 93.8 0.4 Sep 70.6 71.7 1.1 Sep 88.0 88.7 0.7 Oct 66.7 68.1 1.4 Oct 77.8 78.1 0.3 Nov 61.3 62.7 1.4 Nov 65.7 65.5 -0.2 Dec 56.5 57.9 1.4 Dec 57.6 57.0 -0.6 Ann 63.6 64.7 1.1 Annual 75.8 76.0 0.2 The New Normal—SoCal Edition—cont’d Precipitation Change in 30—year Normals Change Precipitation was lower by precipitation 1981- 1991- a little or quite a lot (1 to 31 per- normals +/- inch % cent, see chart at right). This is 2010 2020 not surprising when the average L.A. Downtown 14.93 14.25 -0.68 -5% annual precipitation in places like the desert is only a few inches. Fullerton 13.88 11.86 -2.02 -15% Another interesting way to John Wayne AP 13.33 11.18 -2.15 -16% look at the precipitation trends are how normals have changed Riverside 10.33 10.02 -0.31 -3% over many decades. We did a sim- Elsinore 12.44 11.65 -0.79 -6% ple tally of monthly and annual rainfall at San Diego, a compari- Oceanside 13.66 11.86 -1.80 -13% son of the 30 year average rain- Ramona 16.04 14.65 -1.39 -9% fall recalculated every ten years (see chart below). It deserves a San Diego 10.34 9.79 -0.55 -5% closer analysis to draw out some El Cajon 12.31 11.63 -0.68 -5% conclusions from the data, but we know that the 1980s were quite Big Bear Lake 20.10 19.98 -0.12 -1% wet compared to the 2010s. Idyllwild 26.18 24.45 -1.73 -7% Another interesting note about San Diego’s rainfall is that Cuyamaca 33.41 30.25 -3.16 -9% the new normals bear out the shorter, sharper rainy season that Victorville 6.15 5.57 -0.58 -9% many climate scientists have Palm Springs 5.74 4.61 -1.13 -20% identified. This includes drier springs and falls in general, simi- Thermal 3.20 2.96 -0.24 -8% lar or slightly wetter winters, and Imperial 3.44 2.38 -1.06 -31% no meaningful change to the already bone dry summers. To learn more, you can read the study: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021GL092843

Comparison of normal rainfall in San Diego from the normals calculated in 1990, 2000, 2010 and 2020. Note the drier springs and falls, with no meaningful trend in winter and summer. Aviation Forecasting and Support at NWS San Diego by Brandt Maxwell, Meteorologist and Aviation Program Manager Have you ever been on an airplane about to land at an airport and looked out the window and saw something like this (below right)? If so, you were probably a little bit worried about whether the plane would be able to land safely in the thick fog, or if you would be diverted to another airport at the last minute! Somebody has to make that decision as to whether or not it is safe to land the plane at an airport, and that is where the National Weather Service (NWS) can help by providing the support to the airport and the pilot. The NWS has a long his- tory of supporting its aviation partners. The United States View of Downtown San Diego from above during a foggy night. Weather Bureau, began its aer- Photo courtesy of KFMB-TV. ological section in 1914, just 13 years after the first manned flight by the Wright Brothers, to provide weather information and forecasts to the rapidly growing aviation community. The first pub- lished aviation weather forecast was issued for the Aerial Mail Service route from New York to Chi- cago on December 1, 1918. These early forecasts were very primitive as there were no satellites to view the storms, no radar to view the precipitation, no balloon soundings to detect the wind, temperature or humidity where the planes flew, and no weather models to see tomorrow’s chang- ing weather. There were only observations taken on the ground, mainly at airports, and word-of- mouth pilot reports that were used to make the forecasts that were critical for aviation. Even “kite stations,” weather instruments attached to airplanes, were not used by the U.S. Weather Bureau until 1931. Forecasters had lim- ited information about weather phe- nomena like thunderstorms, wind shear, fog, icing or turbulence, which obviously had big impacts on aviation. Read more about the early days of aviation weather in the United States: https://celebrating200years.noaa.gov/ foundations/aviation_weather/ welcome.html#get We have come a long way in the over 100 years since those very first aviation forecasts. We have so many tools available, and we can receive the information needed to make a forecast An early Signal Service weather map from September 1, very quickly. There are not only satel- 1872, on record in the NOAA Library. Careful compilation lite images, but many ways to sample and study of these maps led to scientific forecasting. Aviation Forecasting and Support —cont’d the temperature, wind and moisture in the atmosphere by both the geostationary and polar- orbiting satellites. We have far more observations, both at the surface and aloft, including those taken from airplanes. Radar helps us with forecasting and warnings in so many ways, especially during critical weather which can cause problems to airports and the planes that fly between them. And don’t forget the weather models, including high-resolution models (a few of which have a horizontal resolution of less than one mile) and ensembles (models which run over and over again for the same area and time period to help us assess the possibilities and probabilities of the weather that we need to forecast). Meteorologists at each of the 122 NWS Forecast Offices, including San Diego, write technical weather forecasts, called Terminal Aerodrome Forecasts (TAFs) tailored to the airports. Many offices also produce Airport Weather Warnings which are issued for hazards that affect the ground operations, such as lightning, strong winds or hail. When this product is issued, not only do the airport operations personnel receive automated emails, but we call them directly to make sure they are aware of the impending hazard and to offer to answer questions. We also have an aviation weather discussion, where we can write about anything we think might be important to the aviation community, including the confidence level of our forecast. Our TAFs are very technical. These are forecasts that provide very specific Locations where Terminal Aerodrome Forecasts (TAFs) information about the wind direction (to are created by the NWS in San Diego (in blue) and the the nearest 10 compass degrees) and NWS in Oxnard (in red). speed, cloud height (to the nearest 100 feet in most cases), visibility and items like wind shear, precipitation or thunderstorms when expected. San Diego does forecasts for 7 airports in southern California, including airports at San Diego, Carlsbad, John Wayne (Orange County), Ontario, San Bernardino, Palm Springs and Thermal. We also occasionally need to back up the Oxnard NWS office (due to emergencies, or more frequently computer maintenance), and we can (infrequently) back up the Hanford, Seattle and (soon) Honolulu NWS offices. An example of a TAF is below: The NWS Forecast Offices are not the only places that write NWS aviation forecasts. There are 21 Center Weather Service Units (CWSUs), which are NWS offices co-located with the Air Route Traffic Control Centers (the FAA facility responsible for airplanes that are en route at or near their cruising alti- tudes). They provide direct support to the FAA controllers about any hazardous weather in their respective regions. Southern California’s CWSU is in Palmdale, which supports mostly southern California and southern Nevada) and coordi- nates forecasts with the NWS Forecast Offices. The biggest aviation office is the Aviation Weather Center in Kansas City, Missouri, which provides aviation weather support for the entire country as Aviation Forecasting and Support—cont’d well as for many flight routes around the world. This includes forecasts for thunderstorms, turbulence (including clear air turbulence), fog and other hazards to aviation. While most pilots get their flight briefings from the Federal Aviation Administration, the NWS in San Diego will give informal weather briefings for those who request it by phone. Usually the pilots want to know if the weather conditions will be good enough so that they can safely fly, and while we can’t tell them if they can fly or not, we can give them the expected conditions (and the confidence level of that forecast!) so that they can better plan a safe flight. We also visit our partners, or sometimes they will come visit our office. Except during COVID, we visit some of our airports each year, especially our largest one, San Diego International Airport, but we will also occasionally visit some of the lesser known airports. When we visit the airports, we usually meet with the tower personnel and the airport operations staff so that we can hear their weather-related concerns and discuss how we can best mitigate them. They almost always have great stories to tell us; after all, airports are places with a lot of activity! We also visit the Southern California TRACON annually, here in San Diego, a Federal Aviation Administration (FAA) facility where planes are monitored and directed during the approaches towards southern California airports as well as those which have recently taken off, as well as the Air Route Traffic Control Center in Palmdale, which monitors and directs planes over mostly southern California and southern Nevada which are at or near their cruising altitude. We also occasionally offer aviation partner workshops where we can discuss aviation weather concerns as a group, and representatives from the airlines, including meteorologists and dispatch- ers, attend those workshops as well as people from our local airports. We just had an aviation partner workshop in June (2021), which was virtual, but that might have helped more people attend since they could join us from their own home or office. We also do outreach as well (at least during normal times), so we can meet with the general public. Our favor- Outreach visit by the National Weather Service to Ontario Interna- ite places to do aviation out- tional Airport. Photo James Brotherton. reach are the air shows, such as the Miramar Air Show, Riv- erside Air Show or the Great Pacific Air Show in Huntington Beach (where we even give weather briefings to support the safety of the flight operations). We also have given weather safety talks to pilot organizations, and not just for pilots of airplanes but also hot-air balloons! If you have any questions about the aviation forecasting and support we do in San Diego, feel free to send me an email at [email protected]. We’re always glad to hear from you!

Annual San Diego County Wildland Fire Exercise by Alex Tardy The annual San Diego County Wildland Fire exercise was held in May 2021. The 3-day exercise brings in all fire and emergency responding agencies (police, fire, medical services), local, state, and federal to participate in live briefings and strike team training. The fire equipment is strategi- cally located following each morning briefing and hoses are laid out as if there were actual wildfires. There are also small live fire simu- lations for training purposes and demonstra- tions of daily wind and humidity impacts on behavior. This year, Bruno Rodriguez (IMET trainee) and Alex Tardy (Warning Coordina- tion Meteorologist) provided the in-person IMET trainee Bruno Rodriguez gets to meet key and virtual weather briefings. In addition, leaders of the City of San Diego Fire and Emergency NWS San Diego provided daily one-page brief- Management. Every opportunity to meet a partner ings for inclusion in the Incident Action Plan. virtual or in person is one step closer to a relation- This year’s exercise was hosted by ship and trust. Photo Alex Tardy. MCAS Miramar in San Diego. One of the goals of the drill was to establish better communication and relationships prior to the core of the fire season. 2021 has already started out active with at least one wildfire burning over 5000 acres in San Diego County and many smaller burns.

Outlook for the Rest of Summer and Early Fall

Basically, it’s going to be hotter and drier than normal all over the West, leading to worsening drought conditions.

Good thing the monsoon precipitation got a good early start in July for the Southwest. Quarterly Summary April San Diego - Lindbergh Field Data - April April started out with a blast, as in a blast of hot weather on the first of the month. A Santa Ana Max Min Avg Rain pattern brought temperatures of 80s and 90s, and some record daily temperatures to the region, includ- Actual 69.9 57.6 63.8 0.07 ing an impressive 88-degree reading at San Diego. A low pressure trough to the south sent mois- Normal 68.8 57.1 62.9 0.65 ture into the region, enough to produce isolated thunderstorms from Oceanside, on a path north to the San Anomaly 1.1 0.5 2.0 -0.58 Bernardino Mountains. Dry lightning sparked small % of normal 11 fires in Oceanside and in the mountains north of San Bernardino. Max 88 60 0.05 The pattern quickly settled into a seasonal one on the 2nd with a rebuilding marine layer and weak Min 62 51 high pressure aloft. A trough of low pressure pushed through the interior West on the 5th and 6th, bringing strong onshore winds and cooler weather to the region. A weak ridge followed. This seasonal pattern continued for several days. A deeper trough settled over the West on the 13th and 14th, bringing light precipitation to most of Southern Cali- fornia, generally less than one- quarter inch, and most popu- lated areas received less than one-tenth inch. As this trough dove through the Southwest, offshore Santa Ana flow returned to boost temperatures again on the 18th and 19th when 80s Standing lenticular clouds looking east from Rancho Bernardo on 7 and 90s were again common at April. Photo Elizabeth Schenk. lower elevations. Some winds in the coastal foothills gusted 20-40 mph from the northeast. From the 21st through the 23rd, a new trough pushed through California, bringing another round of very light precipitation. Mountain foothills received up to 0.40 inch, while lower elevations received less than one-tenth inch. A deep low-pressure trough dove down the West Coast on the 26th and 27th and generated precipitation across the region, and light mountain snow. Greatest amounts were 0.79 at Paivika Ridge (near Crestline), around 0.50 inch in the western slopes of the mountains, a few hundredths to about one-third inch in the coast and valleys, and a trace to a few hundredths in the deserts. Thunderstorms were observed moving through Scripps Ranch and Poway, and from Hemet south to Fallbrook. Up to one inch of snow was observed in the mountains above 7,000 feet. In the wake of that system, Santa Ana conditions and quickly building high pressure aloft brought a rapid warmup to the region from the 28th to the 30th. Temperatures soared on the 29th and 30th, into the 90s for inland areas, and exceeded 100 in the lower desert. Many daily records were set. Precipitation for the month ranged from less than 20% for most areas to nearly 40% for the mountains of San Diego County. For the water year (starting 1 Oct), stations across the region were running roughly 20 to 60% of normal. Temperatures averaged 1, to nearly 6 degrees Fahrenheit above normal for the month. The lower deserts registered 5 to 6 degrees above average while the coast was 1 to 3 degrees above. Quarterly Summary—continued May San Diego - Lindbergh Field Data - May May followed a very seasonal, springtime pattern of weak troughs and weak ridges alternating Max Min Avg Rain through the region, except for more extreme days late in the month. Actual 69.0 60.6 64.8 0.07 A light rain or drizzle event produced measura- ble rain of less than a few hundredths of an inch Normal 69.5 60.0 64.8 0.28 mainly in San Diego County on the 2nd. Higher pressure followed, with temperatures Anomaly -0.5 0.6 0.0 -0.21 that climbed a little above normal. A trough of low % of normal 25 pressure came through the state on May 7-8, which boosted winds in the mountains and deserts, but Max 76 63 0.04 brought no precipitation. A weak trough was followed by a weak ridge Min 65 54 through the middle of the month. On the 16th through the 17th, a deeper trough passed through the region, producing showers that favored the foothills, but greatest amounts were less than one half inch. A few low maxi- mum temperature records fell on the 17th. An even deeper, colder trough slowly dragged through the region from the 20th to the 23rd. This brought some convective showers to the San Bernardino Mountains, but amounts were around one tenth inch or less. It was unseasonably cool, with some low minimum temperature records met or broken on the 23rd. Strong high pressure quickly built aloft and a touch of offshore flow helped boost temperatures to record levels for a few spots on the 24th, just one day after the low minimum temperature rec- Light snow fell on the Big Bear area ski resorts on the morning ords. That warm air mass led to of 22 May. Image Snow Summit webcam. some high minimum temperature records the next couple nights. The extreme oscillation settled down for the rest of the month, reestablishing the seasonal- ly dominating May Gray pattern. Precipitation for the month ranged from 0% to around 40%. For the water year (starting 1 Oct), stations across the region were running roughly 20 to 60% of normal. Temperatures averaged about as precisely normal as possible, ranging between 1 degree Fahrenheit above or below normal for the month.

June The May gray situation continued into the June gloom season, but only for about the first day. High pressure aloft built during the first few days of the month, bringing very hot inland weather to the region, particularly in the high desert, and diminishing the marine layer. Temperatures in Apple Valley topped out at 104 degrees on the 2nd and at 111 in Ocotillo Wells on the 5th. Low pressure broke down the high and rebuilt the marine layer on the 6th and 7th. Quarterly Summary—continued

This brought heavy drizzle and light rain to San Diego - Lindbergh Field Data - June coastal areas, especially in southern Orange County and in northern San Diego County. With weakening low pressure the next few Max Min Avg Rain days, temperatures settled down to seasonal nor- Actual 72.9 63.6 68.2 0.01 mals with a dominant marine layer near the coast. Normal 71.7 62.6 67.2 0.05 High pressure rebuilt on the 14th and 15th, which brought another inland heat wave. This one Anomaly 1.2 1.0 1.0 -0.04 brought a dry heat to the deserts to the tune of 123 degrees in Palm Springs on the 17th, tying % of normal 20 the highest reading on record. It was also 123 at Max 87 67 0.01 Ocotillo Wells on the 17th and 18th. In Idyllwild the mercury topped out at 104 degrees and in Ap- Min 67 57 ple Valley it reached 112 on the 16th. San Jacinto reached 107 while Yorba Linda got to 97 on the 15th. That strong high pressure ridge hung around the West for several more days. A weak low pressure trough on the West Coast began to weaken the ridge on the 21st and 22nd, bringing the summer heat back down to earth. That pattern lasted until high pressure rebuilt once again on the 26th and 27th. This ridge was the one that was the strongest ever seen in the Pacific Northwest region. Portland, Oregon broke records three days in a row, hitting 108 on the 26th, the highest reading on record. The record lasted one day as they hit 112 on the 27th, then 116 on the 28th. A completely unprecedented event for the entire region. Wildfires that usually wait for August to get going were burning and spreading in late June, also in unprecedented fashion. Back in SoCal, temperatures reached over 100 degrees in the Inland Empire and 120 in the Coachel- la Valley, not quite as extreme as the previous heat wave in mid-June. GOES-17 visible satellite image of the As the high weakened during the last days of weak low that brought light rain and the month, temperatures went down, but remained drizzle to coastal areas on 6-7 June. above normal.