Weather in Kolkata in September

A hard month. September is a hard month in Kolkata, and worth planning around. You should expect rain on 24 days of the month, which is more days wet than dry.

September ranks 7 of 12 in Kolkata: past the worst of the year but short of December, which is the month to book if the dates are open.

Rain on 24 of the month's 30 days, 8 of them heavy. At that frequency a wet-weather backup is not a contingency, it is the itinerary — book the indoor things first and treat the clear days as the bonus. Natural fibres and a second shirt for the day. At 89% nothing dries, including you.

What the averages hide

Averages flatten a month, and this one hides a few things: 20 days top 30 °C, making the heat continuous rather than occasional; the day barely swings — 5 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 33.6 °C and the coldest night fell to 21.9 °C, and the wettest single day dropped 172 mm — roughly 66% of the month's rain in one day.

September is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest September on record still delivered 485 mm against 143 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 259 mm average is a reasonable planning figure, not a promise.

Wind is light at 7.1 km/h, so the temperature on the page is close to the temperature on your skin, and humidity at 89% is the real story though — it is the number that decides how the day feels, not the 30.5 °C.

How September sits in the year

Temperatures hold steady either side: 31 °C in August, 30.5 here, 29.8 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 10 days less of it, so pushing the dates later buys drier weather.

Daylight in September

12.3 hours of daylight, losing 0.6 hours across the month. That is between Kolkata's extremes of 13.5 and 10.8 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 28.3 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Kolkata versus nearby

If Kolkata is one option among several, the nearby comparison is worth making. Jamshedpur is close enough to be a coin toss — within a degree on temperature, 2 days less rain. Ranchi is a better bet in September — 2.6 °C cooler, 3 days less rain.

So: September is a compromise. December is 57 points better and is what Kolkata is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Kolkata

See all twelve months in Kolkata, or where else to go in September.