Climate of Kolkata

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).[1] 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.[1] 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).[1] 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).[2]

Kolkata
Climate chart (explanation)
J F M A M J J A S O N D     17     25 13     23     30 17     33     34 22     48     36 25     102     36 26     260     34 27     332     32 26     329     32 26     296     32 26     151     32 24     26     30 20     17     27 15 Average max. and min. temperatures in °C Precipitation totals in mm Source: IMD
Imperial conversion J F M A M J J A S O N D     0.7     76 56     0.9     85 62     1.3     93 71     1.9     97 77     4     97 80     10     93 80     13     90 79     13     90 79     12     90 78     6     89 75     1     86 67     0.7     81 58 Average max. and min. temperatures in °F Precipitation totals in inches

Rains brought by the Bay of Bengal branch of South-West monsoon[3] lash the city between June and September and supplies the city with most of its annual rainfall of 1,582 mm (62.3 inches). The highest rainfall occurs during the monsoon in August (306 mm). The city receives 2,528 hours of sunshine per annum, with the maximum sunlight occurring in March.[4] Pollution is a major concern in Kolkata, and the Suspended Particulate Matter (SPM) level is high when compared to other major cities of India,[5][6] leading to regular smog and haze. Severe air pollution in the city has caused rise in pollution-related respiratory ailments such as lung cancer.[7]

Climate data for Kolkata (Alipore) 1981–2010, extremes 1901–2012
Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Record high °C (°F)	32.8 (91.0)	38.4 (101.1)	41.1 (106.0)	43.3 (109.9)	43.7 (110.7)	43.9 (111.0)	39.9 (103.8)	38.4 (101.1)	38.9 (102.0)	39.0 (102.2)	34.9 (94.8)	32.5 (90.5)	43.9 (111.0)
Mean maximum °C (°F)	29.8 (85.6)	33.5 (92.3)	37.4 (99.3)	38.5 (101.3)	38.8 (101.8)	38.0 (100.4)	35.9 (96.6)	35.0 (95.0)	35.3 (95.5)	35.1 (95.2)	32.9 (91.2)	29.8 (85.6)	39.8 (103.6)
Average high °C (°F)	25.8 (78.4)	29.2 (84.6)	33.5 (92.3)	35.3 (95.5)	35.3 (95.5)	33.8 (92.8)	32.4 (90.3)	32.2 (90.0)	32.4 (90.3)	32.2 (90.0)	30.1 (86.2)	27.0 (80.6)	31.6 (88.9)
Daily mean °C (°F)	20.0 (68.0)	23.6 (74.5)	28.0 (82.4)	30.4 (86.7)	30.9 (87.6)	30.4 (86.7)	29.4 (84.9)	29.3 (84.7)	29.2 (84.6)	28.1 (82.6)	25.0 (77.0)	21.2 (70.2)	27.1 (80.8)
Average low °C (°F)	14.1 (57.4)	17.8 (64.0)	22.4 (72.3)	25.3 (77.5)	26.4 (79.5)	26.8 (80.2)	26.5 (79.7)	26.4 (79.5)	26.0 (78.8)	24.1 (75.4)	19.7 (67.5)	15.2 (59.4)	22.6 (72.7)
Mean minimum °C (°F)	10.7 (51.3)	12.9 (55.2)	17.6 (63.7)	20.4 (68.7)	21.5 (70.7)	23.7 (74.7)	24.3 (75.7)	24.4 (75.9)	23.8 (74.8)	20.6 (69.1)	15.4 (59.7)	11.8 (53.2)	10.4 (50.7)
Record low °C (°F)	6.7 (44.1)	7.2 (45.0)	10.0 (50.0)	16.1 (61.0)	17.9 (64.2)	20.4 (68.7)	20.6 (69.1)	22.6 (72.7)	20.6 (69.1)	17.2 (63.0)	10.6 (51.1)	7.2 (45.0)	6.7 (44.1)
Average rainfall mm (inches)	10.4 (0.41)	20.9 (0.82)	35.2 (1.39)	58.9 (2.32)	133.1 (5.24)	300.6 (11.83)	396.0 (15.59)	344.5 (13.56)	318.1 (12.52)	180.5 (7.11)	35.1 (1.38)	3.2 (0.13)	1,836.5 (72.30)
Average rainy days	1.1	1.7	2.2	3.4	7.0	12.8	17.7	16.9	13.9	7.4	1.3	0.5	85.9
Average relative humidity (%) (at 17:30 IST)	61	54	51	62	68	77	82	83	82	75	67	65	69
Mean monthly sunshine hours	213.9	211.9	229.4	240.0	232.5	135.0	105.4	117.8	126.0	201.5	216.0	204.6	2,234
Mean daily sunshine hours	6.9	7.5	7.4	8.0	7.5	4.5	3.4	3.8	4.2	6.5	7.2	6.6	6.1
Source 1: India Meteorological Department (sun 1971–2000)[8][9][10]
Source 2: Tokyo Climate Center (mean temperatures 1981–2010)[11]

Climate data for Kolkata
Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Mean daily daylight hours	11.0	11.0	12.0	13.0	13.0	13.0	13.0	13.0	12.0	12.0	11.0	11.0	12.1
Average Ultraviolet index	7	9	11	11+	11+	11+	11+	11+	11	9	7	6	9.6
Source: Weather Atlas [12]

References

1. "Weatherbase entry for Kolkata". Canty and Associates LLC. Retrieved 26 April 2006.
2. "kal Baisakhi". Glossary of Meteorology. American Meteorological Society. Archived from the original on 30 August 2006. Retrieved 5 September 2006.
3. Khichar, M.L.; Ram Niwas (14 July 2003). "Know your monsoon". Agriculture Tribune, The Tribune. The Tribune Trust. Retrieved 9 June 2007.
4. "Calcutta: Not 'The City of Joy'". Gaia: Environmental Information System. Retrieved 26 April 2006.
5. Central Pollution Control Board. "Ambient Air Quality in Seven Major Cities During 2002". Ministry of Environment & Forests, Govt of India. Archived from the original on 25 February 2006. Retrieved 26 April 2006.
6. Central Pollution Control Board. "Air quality in major cities on 16–17 March 2006". Ministry of Environment & Forests, Govt of India. Retrieved 26 April 2006.
7. Bhaumik, Subir (17 May 2007). "Oxygen supplies for India police". South Asia. BBC. Retrieved 23 June 2007.
8. "Station: Calcutta (Alipur) Climatological Table 1981–2010" (PDF). Climatological Normals 1981–2010. India Meteorological Department. January 2015. pp. 161–162. Archived from the original (PDF) on 5 February 2020. Retrieved 2 March 2020.
9. "Extremes of Temperature & Rainfall for Indian Stations (Up to 2012)" (PDF). India Meteorological Department. December 2016. p. M237. Archived from the original (PDF) on 5 February 2020. Retrieved 2 March 2020.
10. "Table 3 Monthly mean duration of Sun Shine (hours) at different locations in India" (PDF). Daily Normals of Global & Diffuse Radiation (1971–2000). India Meteorological Department. December 2016. p. M-3. Archived from the original (PDF) on 5 February 2020. Retrieved 2 March 2020.
11. "Normals Data: Kolkata/Alipore - India Latitude: 22.53°N Longitude: 88.33°E Height: 6 (m)". Japan Meteorological Agency. Archived from the original on 2 March 2020. Retrieved 2 March 2020.
12. "Kolkata, India - Climate data". Weather Atlas. Retrieved 4 April 2017.