Kolkata has a Tropical wet-and-dry climate (Köppen climate classification Aw). The annual mean temperature is 24.8 °C (80 °F); monthly mean temperatures range from 15 °C to 30 °C (59 °F to 86 °F). 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. Winter tends to last for only about two and a half months, with seasonal lows dipping to 9 °C – 11 °C (48.2 °F – 51.8 °F) between December and January. The highest recorded temperature is 43.9 °C (111 °F) and the lowest is 3 °C (37.4 °F). Often during early summer, dusty squalls followed by spells of thunderstorm and heavy rains 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).