The climate of Uttar Pradesh (U.P.) is primarily defined as humid subtropical with dry winter (Cwa) type with parts of Western U.P. as hot semi-arid (BSh) type. Alternatively, some authors refer to it as tropical monsoon. Variations do exist in different parts of the large state, however the uniformity of the vast Indo-Gangetic Plain forming bulk of the state gives a predominantly single climatic pattern to the state with minor regional variations. U.P. has a climate of extremes. With temperatures fluctuating anywhere from to in several parts of the state and cyclical droughts and floods due to unpredictable rains, the summers are extremely hot, winters are cold and the rainy season can be either very wet or very dry.
Seasons of Uttar Pradesh
Indian Meteorological Department (IMD) breakdowns the climate of India into the following seasons: Winter Season / Cold Weather Season (January and February) Summer season/ Pre-monsoon season/ Hot weather season/ Thunderstorm season (March, April, May and June) South-west Monsoon/ Summer Monsoon (July, August and September) Post-monsoon or Northeast monsoon or Retreating SW Monsoon season (October, November and December) This classification is primarily Monsoon centric given the vast effect that it casts on the lives and agriculture of India.
Classification of the Uttar Pradesh climate
The climate of Uttar Pradesh is generally defined to be tropical monsoon type. However based on the Köppen climate classification, it can be classified mostly as Humid Subtropical with dry winter (CWa) type with parts of Western U.P. as Semi-Arid (BS) type (refer to map of India above)
Based on IMD classification, UP has the following three predominant seasons: Winter Season – November to February Summer season – March, April and May South-west Monsoon – June, July, August, September and October Retreating Monsoon season, although existent, has a very negligible effect in Uttar Pradesh and only occasional mild showers are experienced in winter. Some of these showers are not even due to the Monsoon but due to western disturbances.
The primary temperature, rainfall and wind features of the three Distinct Seasons of U.P. can be summarised as below: Summer (March–June): Hot & dry (temperatures rise to , sometimes ); low relative humidity (20%); dust laden winds. Monsoon (June–October): 85% of average annual rainfall of . Fall in temperature on rainy days. Winter (November–February): Cool (morning temperatures drop to , sometimes below ); clear skies; foggy conditions in some tracts.
Given significant climatic differences, U.P. has been divided into two meteorological sub-divisions – U.P. East and U.P. West.
Geographical terrain
The state of Uttar Pradesh is in the heart of Indo-Gangetic Plain with River Ganges flowing right through the State, Himalayas to the north and the Chota Nagpur Plateau and the Vindhyas to the south of the State.
Temperature
Temperature varies from . High temperatures of around have been recorded in Gonda district of U.P. Given such a wide range of temperature fluctuations in most parts of the state, it can lead to either cold waves or heat waves both resulting in substantial loss of life and economy.
Heat waves
In 2007, Banda with temperature was the leader in terms of hot districts of U.P. for several days. At least 62, people were reportedly dead during the heat wave that year. In June 2009, 30 people died of heatstroke in U.P. Highest temperatures reached in Bundelkhand district of northern U.P. In June 2010, Jhansi recorded the highest temperature of , the hottest for U.P. for that year.
Cold waves
In recent years, winters at the end of 2007 and beginning of year 2008 caused a string of cold-wave related deaths in U.P. with temperatures as low as in the city of Meerut, U.P. Simultaneously it also led to a loss of crops and agricultural produce. Similarly last part of 2009, saw the mercury-dipping to lows of in Meerut again causing loss of human life. End of 2010 and starting of 2011 was no different with winters bringing news of cold-wave related deaths. This time Churk town in Sonbhadra district ranked coldest with . On 13 January 2013, Kanpur recorded its all-time low temperature when the mercury plunged to and on the same day Agra recorded . In the month of January in Lucknow temperature can plunge below freezing; Lucknow recorded on 18 January 2017. Agra and Muzaffarnagar are also notorious for chilly winds and the temperature there can also go below freezing.