Dhaka receives 1,990 millimetres of rain a year over 118 days, with an annual average humidity of 72 % and 2,225 hours of sunshine. These are wet-tropics figures, and at first glance they suggest a simple calendar: avoid the monsoon. The reality is a little more precise than that, and on one point it is the exact opposite.
01 Two thousand millimetres in four months
The distribution of rain is extreme. From June to September, 315, 390, 315 and 285 millimetres fall, that is, 1,305 of the annual 1,990 concentrated into four months. July and August have twenty-one rainy days each: in practice, it rains almost every day. At the other end, January and December get 5 and 10 millimetres, over a single rainy day each.
02 The hottest month is April
Here is the figure that changes the choice. The year's highest average maximum is neither July's nor August's: it is April's, at 33.9 degrees, followed by May at 33.6. July, the month of torrential rain, stays at 32.1. That is, the monsoon cools things by almost two degrees from the peak.
March, April and May are also the season of strong pre-monsoon thunderstorms, which arrive in the afternoon with wind and heavy downpours while the temperature keeps climbing. The combination of 33.9 degrees, rising humidity and sudden storms is what makes April the month genuinely to avoid.
The monsoon is not the peak of heat: it is what breaks it. July is almost two degrees below April.
03 The dry window
The good window runs from November to February and is surprisingly comfortable. January has highs of 24.6 degrees and lows of 13.3, with five millimetres of rain over a single day. February climbs to 28.3 but humidity drops to 61 %, the year's lowest, which you feel more than the degrees.
One trade-off has to be stated plainly, because it affects your health and appears in no climate table. Those same dry, windless months are when the city's air quality degrades most, through the combination of traffic, construction and stagnant air. If you have asthma or respiratory allergies, check the day's index before planning a full day outdoors.
04 What the monsoon does offer
If your dates fall in the middle of the monsoon, it is worth knowing what you gain and what you lose. You lose predictability: twenty-one rainy days in July means there is no way to plan an outdoor day with any guarantee, and sunshine drops to five hours. You also have to expect occasional urban flooding that jams the traffic for hours.
What you gain is a lower temperature than April's, a river landscape at its most impressive and a city with no other visitors. And there is a serious precaution that does not depend on rain: tropical cyclones have two peaks, from late April to early June and in October and November. Check the forecast before those dates.
05 The verdict
January, by a clear margin. It is the only month combining highs of 24.6 degrees, a single rainy day in the whole month and a low of 13.3 that lets you sleep without air conditioning. December is practically as good and a little cooler at night.
And the rule that sums up the whole article: if you have to choose between going in April and going in July, go in July. You will get far wetter, but you will be less hot, and in a climate like this the difference between 33.9 and 32.1 degrees with rising humidity registers in the body far more than the number suggests.
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