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 the 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 0 °C or 32 °F to 50 °C or 122 °F 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:^[1][2]

1. Winter Season / Cold Weather Season (January and February)
2. Summer season/ Pre-monsoon season/ Hot weather season/ Thunderstorm season (March, April, May and June)
3. South-west Monsoon/ Summer Monsoon (July, August and September)
4. 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.^[3] 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:^[4][5]

1. Winter Season – November to February
2. Summer season – March, April and May
3. 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.^[6]

The primary temperature, rainfall and wind features of the three Distinct Seasons of U.P. can be summarised below:

1. Summer (March–June): Hot & dry (temperatures rise to 45 °C or 113 °F, sometimes 47 or 48 °C or 116.6 or 118.4 °F); low relative humidity (20%); dust laden winds.
2. Monsoon (June–October): 85% of the average annual rainfall of 990 millimetres or 39 inches. Fall in temperature on rainy days.
3. Winter (November–February): Cool (morning temperatures drop to 3–4 °C or 37.4–39.2 °F, sometimes below −1 °C or 30.2 °F); 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.^[7]

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 0 to 46 °C (32.0 to 114.8 °F).^[5] High temperatures of around 50 °C or 122 °F have been recorded in Gonda district of U.P.^[3] 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 45.5 °C or 113.9 °F temperature was the leader in terms of hot districts of U.P. for several days.^[8] At least 62, people were reportedly dead during the heat wave that year.^[9] In June 2009, 30 people died of heatstroke in U.P.^[10] Highest temperatures reached 49 °C or 120.2 °F in Bundelkhand district of northern U.P.^[11][12] In June 2010, Jhansi recorded the highest temperature of 46.7 °C or 116.1 °F, the hottest for U.P. for that year.^[13]

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.^[14] with temperatures as low as 2.8 °C or 37.0 °F 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 2.9 °C or 37.2 °F in Meerut again causing loss of human life.^[15] The end of 2010 and starting of 2011 were no different, with winters bringing news of cold-wave-related deaths.^[16][17] This time Churk town in Sonbhadra district ranked coldest with 1.4 °C or 34.5 °F.^[16] On 13 January 2013, Kanpur recorded its all-time low temperature when the mercury plunged to −1.1 °C or 30.0 °F and on the same day Agra recorded −0.7 °C or 30.7 °F. In the month of January, in Lucknow, the temperature can plunge below freezing; Lucknow recorded 0.0 °C or 32.0 °F on 18 January 2017. Agra and Muzaffarnagar are also notorious for chilly winds and the temperature there can also go below freezing.

Precipitation

It rains over most of the U.P., with very few arid or semi-arid patches. Snowfall doesn't occur, but hail-storms, frost, and dew occur often in U.P. The type of rainfall that U.P. receives is orographic, cyclonic and convectional.^[5]

Rain

Primarily a summer phenomenon, the Bay of Bengal branch of the Indian Monsoon is the major bearer of rain in most parts of U.P. It is the South-West Monsoon which brings most of the rain here, although rain due to the western disturbances^[6] and North-East Monsoon also contribute small quantities towards the overall precipitation of the state.^[5] The rain in U.P. can vary from an annual average of 170 cm in hilly areas to 84 cm in Western U.P.^[5] Given the concentration of most of this rainfall in the 4 months of Monsoon period, excess rain can lead to floods and shortage to droughts.^[3] As such, these two phenomena of floods and droughts are a common recurrence in the state.

Floods in U.P.

Floods are a known hazard of U.P. due to overflowing of its main rivers like Ganga, Yamuna, Ramganga, Gomti, Sharda, Ghaghra, Rapti and Gandak.^[7] Estimated annual losses due to floods in U.P. is ₹4.32 billion (US$54 million).^[7] Major flood management efforts have been undertaken to mitigate the risk. Most of these floods occur due to the Monsoon rains and overflowing of rivers during the rainy periods. Year 2010 witnessed one such year of flooding in U.P.^[18][19]

Droughts in Uttar Pradesh

Shortage of rain during the highly variable Monsoon season can cause droughts in U.P. leading to severe loss to man and property. Recent 2002 and 2004 drought-related financial estimates have been reported to be ₹75.4 billion (US$940 million) and ₹72.92 billion (US$910 million).^[7] The recurrence of a major deficiency in annual rainfall follows a 6–8-year cycle in Eastern U.P., whereas in Western U.P., it is a 10-year cycle.

Wind

In summer, hot winds called loo blow all across U.P. They are dust-laden and quite damaging.^[5] In winter, dry and rainless winds blow across the state. Fog may also form in parts of U.P.^[5]

Climate data