Kolkata has a Tropical wet-and-dry climate (

Köppen climate classification The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, nota ...

''Aw''). The annual mean temperature is 26.8 °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 5 °C (41 °F). Often during early summer (mid March to mid May), dusty squalls followed by spells of

thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are some ...

and heavy rains lash the city, bringing relief from the humid heat. These thunderstorms are

convective Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the ...

in nature, and is locally known as ''Kal baisakhi'' (, Nor'westers). Rains brought by the Bay of Bengal branch of South-West

monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...

lash the city between June and September and supplies the city with most of its annual rainfall of 1,836.5 mm (72.30 inches). The highest rainfall occurs during the monsoon in July and August interchangeably. The city receives 2578 hours of sunshine per annum, with the maximum sunlight occurring in March.

Pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, th ...

is a major concern in Kolkata, and the Suspended Particulate Matter (SPM) level is high when compared to other major cities of India, leading to regular

smog Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words '' smoke'' and ''fog'' to refer to smoky fog due to its opacity, and odor. The word was then int ...

and

haze Haze is traditionally an atmospheric phenomenon in which dust, smoke, and other dry particulates suspended in air obscure visibility and the clarity of the sky. The World Meteorological Organization manual of codes includes a classificati ...

. Severe air pollution in the city has caused rise in pollution-related respiratory ailments such as lung cancer. {{Kolkata weatherbox

Weather Monitoring Stations

Alipore Alipore (Pron:ˌɑ:lɪˈpɔ:) is a neighbourhood in south Kolkata, in Kolkata district, in the Indian state of West Bengal. It is flanked by the Tolly Nullah to the north, Bhowanipore to the east, the Diamond Harbour Road to the west and ...

is the major station, which is an international station. But there are also two stations at Dum Dum and

Salt Lake A salt lake or saline lake is a landlocked body of water that has a concentration of salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of salt per litre) ...

References

Kolkata Kolkata (, or , ; also known as Calcutta , the official name until 2001) is the capital of the Indian state of West Bengal, on the eastern bank of the Hooghly River west of the border with Bangladesh. It is the primary business, comme ...

Geography of Kolkata