The state is wedged between the Lakshadweep Sea and the . Lying between north latitudes 8°18' and 12°48' and east longitudes 74°52' and 77°22',[91] experiences the humid equatorial tropic climate. The state has a coast of 590 km (370 mi)[92] and the width of the state varies between 11 and 121 km (22–75 miles).[93] Geographically, Kerala can be divided into three climatically distinct regions: the eastern highlands; rugged and cool mountainous terrain, the central mid-lands; rolling hills, and the western lowlands; coastal plains.[94] The state is located at the extreme southern tip of the Indian subcontinent and lies near the centre of the Indian tectonic plate; hence, it is subject to comparatively low seismic and volcanic activity.[95] Pre-Cambrian and Pleistocene geological formations compose the bulk of Kerala's terrain.[96][97] A catastrophic flood in Kerala in 1341 CE drastically modified its terrain and consequently affected its history; it also created a natural harbor for spice transport.[98]

The eastern region of Kerala consists of high mountains, gorges and deep-cut valleys immediately west of the Western Ghats' rain shadow.[94] Forty-one of Kerala's west-flowing rivers,[99] and three of its east-flowing ones originate in this region.[100][101] The Western Ghats form a wall of mountains interrupted only near ; hence also known Palghat, where the Palakkad Gap breaks through to provide access to the rest of .[102] The Western Ghats rise on average to 1,500 m (4920 ft) above sea level,[103] while the highest peaks reach around 2,500 m (8200 ft).[104] , the highest peak in , is at an elevation of 2,695 metres (8,842 ft).[105] The elevations of the eastern portions of the Nilgiri Hills and Palni Hills range from 250 and 1,000 m (820 and 3300 ft).[106][107] Tipu Sultan's fort at Palakkad; view from outside the northern wall. Kerala's western coastal belt is relatively flat to the eastern region,[108] and is criss-crossed by a network of interconnected brackish canals, , estuaries,[109] and rivers known as the .[110] The state's largest , dominates the Backwaters; it lies between and and is more than 200 km2 (77 sq mi) in area.[111] Around 8% of India's waterways are found in Kerala.[112] Kerala's forty-four rivers include the ; 244 km, Bharathapuzha; 209 km, Pamba; 176 km, ; 169 km, Kadalundipuzha; 130 km, Chalakudipuzha; 130 km, Valapattanam; 129 km and the River; 128 km. The average length of the rivers is 64 km. Many of the rivers are small and entirely fed by rain.[113] As Kerala's rivers are small and lacking in delta, they are more prone to environmental effects. The rivers face problems such as sand mining and pollution.[114] The state experiences several natural hazards like landslides, floods, lightning and droughts; the state was also affected by the 2004 Indian Ocean Tsunami.[115]