Asansol's climate is hot for most of the year and uncomfortable in May and June, with daytime temperatures regularly above 40°C and dust from the surrounding coalfields hanging in the air. The monsoon (June to September) brings heavy rain but cooler nights, and the rivers behind the dams fill up — best season for the Maithon and Panchet excursions, even if the road can be slow.
November to February is the time to come. Days are bright, nights are cool, the air over the city is much cleaner, and the religious festivals — Kali Puja in October–November, Durga Puja a little earlier — fall in this window. Avoid March to early June unless you have to be here for business.