Climate Projections for the Okanagan Region February 2020 In partnership with Chapter 3 – Summer Temperature Indicators ..................... 17 Days Above 30°C ......................................................................................................18 Table of Contents Hottest Days .............................................................................................................. 20 1-in-20 Hottest Day ..................................................................................................21 Growing Season Length.......................................................................................21 Chapter 1 – Introduction ............................................................ 5 Cooling Degree Days ............................................................................................22 How Much Will the Climate Change? .......................................................... 6 Shifting Seasons .........................................................................................................7 Chapter 4 – Winter Temperature Indicators .......................23 A Note on Data Interpretation ............................................................................7 Average Spring Nighttime Low Temperatures ....................................24 Coldest Night ..............................................................................................................26 Chapter 2 – Regional Impacts ..................................................9 Frost Days .....................................................................................................................26 Past Climate Events ................................................................................................10 Ice Days .......................................................................................................................... 27 Ecosystems and Biodiversity ............................................................................11 Heating Degree Days ............................................................................................29 Health ...............................................................................................................................13 Water Quantity and Quality ................................................................................13 Chapter 5 – Precipitation Indicators .....................................31 Total Precipitation ...................................................................................................32 Transportation Infrastructure ..........................................................................14 Wettest Day .................................................................................................................35 Stormwater Infrastructure .................................................................................14 Wettest 5 Days ..........................................................................................................35 Recreation .....................................................................................................................14 1-in-20 Wettest Day ............................................................................................... 36 Agriculture .....................................................................................................................15 Precipitation on Wet Days and Very Wet Days ....................................37 Local Economy ...........................................................................................................16 Buildings and Energy Systems .......................................................................16 Chapter 6 – Conclusion ...........................................................39 Appendix 1: Methodology ........................................................41 Appendix 2: Maps by Regional District ................................43 Climate Model Selection ....................................................................................42 Section A: Maps for Regional District Indicator Derivation ...............................................................................................42 of North Okanagan (RDNO) ..............................................................................44 Interpretation .............................................................................................................42 Section B: Maps for Regional District of Central Okanagan (RDCO) ..........................................................................50 Section C: Maps for Regional District of Okanagan-Similkameen (RDOS)............................................................ 56 List of Figures List of Tables Figure 1: Future Temperature by Emissions Table 1: Change in Summer Days Above 30°C ......................................18 Scenario for BC ........................................................................................................... 8 Table 2: Change in Hottest Day (TXx) ........................................................ 20 Figure 2: Understanding the Variable Path Table 3: 1-in-20 Hottest Day (RP20 TX) .......................................................21 of Climate Change .................................................................................................... 8 Table 4: Change in Growing Season Length ..........................................22 Figure 3: Days Above 30°C – Past .................................................................19 Table 5: Change in Cooling Degree Days ................................................22 Figure 4: Days Above 30°C – Future (2050s) ..........................................19 Table 6: Change in Average Spring Nighttime Lows .......................24 Figure 5: Spring Nighttime Lows – Past ...................................................25 Table 7: Change in Coldest Nights ................................................................26 Figure 6: Spring Nighttime Lows – Future (2050s) ...........................25 Table 8: Percent Change in Frost Days, Annually .............................. 27 Figure 7: Ice Days – Past .....................................................................................28 Table 9: Change in Ice Days ............................................................................. 27 Figure 8: Ice Days – Future (2050s) .............................................................28 Table 10: Percent Change in Heating Degree Days ..........................29 Figure 9: Autumn Precipitation – Past ......................................................34 Table 11: Seasonal Precipitation .....................................................................33 Figure 10: Autumn Precipitation – Future (2050s) .............................34 Table 12: Wettest Days Indicators ................................................................ 36 Figure 11: Autumn Precipitation Table 13: Change in Wet Days and Very Wet Days ............................37 – Percent Change (2050s) ................................................................................35 Figure 12: Wet Days – Past ................................................................................ 38 Figure 13: Wet Days – Future (2050s) ........................................................ 38 Climate Projections for the Okanagan Region | 1 Acknowledgements This work offers climate projections for the Okanagan region, which is located within the Traditional Territories of the Syilx Okanagan Nation and the Splatsin Band of the Shuswap Nation. This report is a collaboration between the Regional District of North Okanagan (RDNO), the Regional District of Central Okanagan (RDCO), and the Regional District of Okanagan-Similkameen (RDOS) that would not have been made possible without the participation of nearly 90 stakeholders from across the region, the support of Trevor Murdock, Steve Sobie, and Kari Tyler from the Pacific Climate Impacts Consortium in providing climate data and interpretation, and Gillian Aubie Vines, who served as the project facilitator and lead writer for this project. This project was made possible with support from Natural Resources Canada through the Adaptation Platform, Okanagan Basin Water Board and Fraser Basin Council. 2 | Executive Summary Climate change is challenging ecosystems, communities, and the economy. Wildfires, flooding, and drought have already overwhelmed local infrastructure, caused economic losses, and posed health risks to communities. Significant effort to reduce the reliance on fossil fuels as quickly as possible will slow, and has the potential to curb, climate change by the late century, making greenhouse gas emissions reductions a central part of any long-term adaptation strategy.1 Designing to current and future climate parameters is markedly more cost effective than reacting to climate shocks and stresses over time. This report is intended to support a local understanding of how climate across the Okanagan is projected to change, and inform regional planning on how to prepare for future climate events. This work is critical to maintaining wellbeing, including robust ecosystems, a thriving community, and a vibrant economy. Early efforts to prepare infrastructure and communities to climate change will reduce regional reliance on continued emergency management activations and support the ability of the region to thrive over time. Summers are getting hotter by the later part of the century, the valley bottoms,