Patna, the capital of Bihar, sits on the southern bank of the Ganges in the eastern Indo-Gangetic plain, near the confluence of several great rivers at approximately 25.61°N, 85.14°E. It has a humid subtropical climate (Köppen Cwa) — with extremely hot pre-monsoon summers, a heavy monsoon and cool winters — and its low-lying riverside position leaves it exposed to serious flooding.

Summer, from March to June, is extremely hot, with May the hottest month — highs regularly above 40°C, and a record of 46.6°C — under a fierce sun, with hot, dry winds early in the season giving way to rising humidity. The monsoon then runs from mid-June to September, when the Ganges runs at full power and the city can receive close to 290 mm of rain in a month.

Winter, from late October to early February, is cool and dry, with December and January the coolest — highs around 23°C but nights that can fall to 7–10°C, and Patna has recorded 0°C. Fog is frequent on cold mornings, skies are otherwise clear, and this dry, cool stretch is comfortably the best time to visit the city.

Patna receives around 1,000–1,100 mm of rain a year, overwhelmingly delivered by the southwest monsoon from mid-June to September, when monthly totals can approach 290 mm, while the rest of the year is very dry. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Patna's position on the low-lying southern bank of the Ganges, close to where several major Himalayan rivers converge, makes flooding its gravest hazard: heavy monsoon rain across the catchment, including in Nepal, can send the rivers over their banks and inundate the city, as in the severe floods that have repeatedly struck Bihar.

To follow any single measurement in Patna 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.