Climate

Kolkata has a tropical wet-and-dry climate (Koppen climate classification Aw). The annual mean temperature is 26.8 °C (80.2 °F); monthly mean temperatures range from 19 °C (66.2 °F) to 30 °C (86.0 °F).^[35] Summers are hot and humid with temperatures in the low 30's and during dry spells the maximum temperatures often exceed 40 °C (104 °F) during May and June.^[35] Winter tends to last for only about two and a half months, with seasonal lows dipping to 9 °C – 11 °C (54 °F – 57 °F) between December and January. The highest recorded temperature is 43.9 °C (111.0 °F) and the lowest is 5 °C (41.0 °F).^[35]On an average, May is the hottest month with daily temperatures ranging from a low of 27 °C (80.6 °F) to a maximum of 37 °C (98.6 °F),while January the coldest month has temperatures varying from a low of 12 °C (53.6 °F) to a maximum of 23 °C (73.4 °F). Often during early summer, dusty squalls followed by spells of thunderstorm or hailstorms and heavy rains with ice sleets lash the city, bringing relief from the humid heat. These thunderstorms are convective in nature, and is locally known as Kal baisakhi (কালবৈশাখী, Nor'westers).^[36]

Rains brought by the Bay of Bengal branch of South-West monsoon^[37] lash the city between June and September and supplies the city with most of its annual rainfall of 1,582 mm (62 in). The highest rainfall occurs during the monsoon in August—306 mm (12 in)). The city receives 2,528 hours of sunshine per annum, with the maximum sunlight occurring in March.^[38] Pollution is a major concern in Kolkata, and the Suspended Particulate Matter (SPM) level is high when compared to other major cities of India,^{[39][40][dead links]} leading to regular smog and haze. Severe air pollution in the city has caused rise in pollution-related respiratory ailments such as lung cancer.^[41]