Kolkata (formerly Calcutta), the capital of West Bengal, sits in the Ganges Delta in eastern India, on the Hooghly River a little inland from the Bay of Bengal at approximately 22.57°N, 88.36°E. It has a tropical wet-and-dry climate (Köppen Aw) with a hot, humid summer, a heavy southwest-monsoon rainy season and a short, mild, dry winter. Its delta setting keeps humidity high for much of the year.

Summer, from March to June, is hot and extremely humid, with highs around 36–38°C and a sweltering, sticky feel from the delta moisture. Late spring brings the Kalbaisakhi or 'Nor'wester' — violent afternoon thunderstorms sweeping in with strong winds, lightning and sudden rain that briefly break the oppressive heat. The southwest monsoon then arrives around mid-June, ushering in the main rains through September.

Winter, from December to February, is short, mild, dry and pleasant, with January the coolest month — highs around 26–27°C and comfortable nights that can dip to 12–14°C. Low humidity, warm sunny days and cool mornings make this comfortably the best time of year, a welcome respite from the long humid heat that dominates the rest of the calendar.

Kolkata is wet, receiving on the order of 1,600–1,800 mm of rain a year, the overwhelming majority delivered by the southwest monsoon between June and September, when July and August are the wettest and heavy downpours regularly cause waterlogging across the low-lying delta city. The winter months are largely dry. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Lying in the low, flat Ganges Delta near the head of the Bay of Bengal, Kolkata is exposed to tropical cyclones, which most often threaten before and after the monsoon and can bring destructive winds, torrential rain and storm surge — Cyclone Amphan struck the city hard in May 2020. The pre-monsoon Nor'westers are the other signature feature, dramatic storms that provide sudden, welcome relief from the building summer heat.

To follow any single measurement in Kolkata more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.