The city receives 669 millimetres of rain a year, of which 371 fall in July and August, and its temperature spans almost fifty degrees between the cold record, −1.3, and the heat record, 47.6. With those numbers, choosing a month looks simple. It is, only until you add a variable that appears in no climate table.
01 The table is not enough
The mechanism is meteorological and worth understanding because it explains the calendar. Between late October and January the air stabilises, the wind drops and an inversion layer forms that acts as a lid: what is emitted over the plain stays down instead of dispersing. Monsoon rain, by contrast, washes the atmosphere every few days.
02 The heat of May
The other end of the year is simpler to explain. May has an average high of 41.2 degrees and a low of 25.5, and the absolute record of the series is 47.6. April is already at 36.8 and June at 40.5. These are three months in which the city, quite simply, cannot be walked between ten in the morning and five in the afternoon.
One nuance helps you choose between April and May: in those months humidity is low, and dry heat at 40 degrees is more bearable than humid heat at 35. The problem arrives in June, when monsoon humidity comes in before the temperature has dropped. That is the calendar's worst combination.
03 The monsoon: two months out of four
The rainfall distribution is textbook monsoon: 69.9 millimetres in June, 182.2 in July, 188.4 in August and 106.1 in September. July and August alone make up 55 % of the annual total. The rest of the year is genuinely dry: November has 2.1 millimetres and December 5.4.
July and August hold 55 % of the year's rain. And they are, precisely, the two months when the air is best.
That leaves the monsoon in an odd position: climatically uncomfortable — high humidity, flooded streets, impossible traffic — but with washed air and a green plain. If your dates are fixed and fall in July or August, the compensation exists and is real; it just is not where you look for it.
04 The fog of January
Winter adds a logistical problem worth bearing in mind when buying tickets. With lows of 7.7 degrees in January and 8.3 in December, loaded air and dawn humidity, episodes of dense fog form that cut visibility to a few metres and cause delays and cancellations at the airport and on the trains.
The practical consequence is simple: if you travel in December or January, do not chain a tight connecting flight and leave margin between train and plane. It is not a theoretical risk; it is the reason January, despite a reasonable table, does not reach the ideal-month category in this guide.
05 The verdict
February, by a clear margin. It has a high of 24.3 degrees and a low of 11.0 — walk-all-day temperature — barely 19.8 millimetres of rain, winter fog already receding and air improving on the November-to-January stretch. March works just as well if you accept 30.7 degrees at midday.
And a practical recommendation for any month: check the day's air quality index before planning a full day outdoors, exactly as you would check the rain forecast. If you have asthma or respiratory allergies, that check matters more here than the thermometer.
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