West Bengal has a varied climate, with tropical savannahs in the southern portions of the state, to humid subtropical areas in the north. Temperatures vary widely, and there are five distinct seasons. The area is vulnerable to heavy rainfall, monsoons, and cyclones. There are some mountains in the area which are generally cold all year round.
There are six main seasons in West Bengal: summer (Grishma), monsoons or rainy season (Barsha), autumn (Sharat), late autumn/pre winter (Hemanta), winter (Sheet), spring (Bawshonto) .
Spring is considered the most pleasant season over the plains of West Bengal and lies from mid-February to mid-March and is also the time where Holi is celebrated. Temperatures range between 20 ðC â 30 ðC and no rainfall. Though occasional rain or light showers are witnessed due to Western disturbances in North India.
The summer season is observed from March to May in most of Bengal.
In Bengal, summers can be extremely hot and have high humidity. The plains of South Bengal have a daily maximum temperature around 35âÂÂ38 ðC. It can also exceed 40 ðC. The western highlands experience a dry summer like northern India. During the day, the temperature ranges from 38 to 42 ðC, though it can reach or exceed 45 ðC. In summer, the plains of North Bengal are generally cooler than the west and south. In this area, the daily maximum temperature varies from 26 ðC to 32 ðC. It occasionally crosses 35 ðC. The minimum temperature in summer is approximately 18âÂÂ22 ðC. The Darjeeling hill region is the coolest area in summer. Here, the daily highest temperature is 15âÂÂ25 ðC.
In mid-June or early July, the monsoon season starts.
In most places, the temperature drops as cloud cover increases. This is less true for the mountains and the Terai Dooars plains, where temperature gradually increases until August.
The maximum temperature of South Bengal's plains and western highlands is 32 ðC, 31 ðC in North Bengal plains and around 19âÂÂ20 ðC in mountains. Sometimes when the sky gets clear, the temperature rises suddenly. This is known as a monsoon break. This occurs mostly in North Bengal plains and in mountains in July and August when the temperature soars over 36 ðC and 24 ðC respectively.
Most of the annual rainfall occurs during the monsoon period. Heavy rainfall above 250 cm is observed in the Darjeeling, Jalpaiguri, Alipurduar and Cooch Behar district. Later, blowing westwards, the winds cause average rainfall of 125 cm in the northern plains and western plateau region.
Autumn lasts for two months, October and November.
In autumn, the southwest monsoon wind returns and clears the sky. So, the state gets enough sunshine to be warm in the day and releases a lot of heat to be cool at night.
At this time, a maximum temperature of 30âÂÂ33 ðC is felt over the plains and 17âÂÂ19 ðC in mountains. The minimum temperature is normally around 19âÂÂ22 ðC in plains and 6âÂÂ11 ðC in mountains. Sometimes, cold waves blow over the state in autumn.
In autumn, the southwest monsoon wind returns, and the northeast monsoon wind enters West Bengal. Due to their collision in Bay of Bengal, some cyclones are created. The cyclones cause some rainfall in the state.
The winter season usually starts in December and ends in February.
In winter, a mild temperature is observed over the plains. The maximum temperature goes to 23âÂÂ26 ðC and the minimum temperature is 9âÂÂ15 ðC in plains of the state. The maximum and minimum temperature in the mountains range from 0âÂÂ12 ðC. Higher regions of the Darjeeling Himalayas get heavy snowfall during winter.
The temperatures of the western highlands at night can drop 7âÂÂ9 ðC, 4âÂÂ7 ðC in Siliguri, Jalpaiguri, Coochbehar plains and 10âÂÂ11 ðC in Kolkata when cold waves blow. Darjeeling's temperature can drop below freezing point.
Winter is generally dry. Most days are sunny. Occasionally, slight rainfall occurs because of conditions in northwest India. These are known as western disturbances.
Sources: India Meteorological Department
The chart below shows the highest recorded temperatures in individual stations, for all months in West Bengal, with place and date.
The chart below shows the lowest recorded temperatures in individual stations, for all months in West Bengal, with place and date.
The chart below shows the lowest recorded temperatures in individual stations in the plains, for all months in West Bengal, with place and date.
The chart below shows the maximum recorded rainfall in individual stations (observatories) in the state, for all months, with place and date.
Annual rainfall varies in different parts of the state. North Bengal receives the highest rainfall, 200 to 400 cm. In the coastal areas rainfall is about 200 cm, in the Ganga plain and in the central part of the state rainfall is about 150âÂÂ200 cm, and in the western plateau region the amount of rainfall received is about 100 to 125 cm. Drought is a common phenomenon in the Bankura and Purulia districts. Rainfall that occurs in the summer months often brings about heavy storms called Kalbaishakhi.
Because of the high altitude, mountainous parts of Darjeeling and Jalpaiguri experience a cool temperate and climate. The average temperature in summer is about , and winter temperature is about . Snowfall occurs in some parts of this region. Being obstructed by the Himalayas, the region receives heavy rainfall. Due to the scenic beauty and temperate climate of the region, a huge number of tourists visit the areas. Here Kalimpong is another hill station that is visited by many tourists in all seasons for its scenic beauty and the average cool temperature throughout the year.