Kolkata has a tropical wet-and-dry climate. 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) The city experience a very humid and warm summers during the months of April to October with temperature reaching up to 42 ‘C. During the winter months the temperature drops to about 9.6 ‘C providing a pleasant weather to enjoy. The highest recorded temperature is 43.9 °C (111.0 °F) and the lowest is 5 °C (41.0 °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. This thunderstorm is convective in nature, and is locally known as Kal baisakhi.
Rains brought by the Bay of Bengal branch of South-West monsoon lash the city between June and September and supplies the city with most of its annual rainfall of 1,582 mm. The highest rainfall occurs during the monsoon in August—306 mm. Severe air pollution in the city has caused rise in pollution-related respiratory ailments such as lung cancer. The best time to visit the city of Kolkata is during the months of November to February.