November to February is the best time to visit Chittagong. Daytime temperatures hover around 25-28°C, the humidity drops, and there is little rain. The smoggy winter haze is less of a problem here than in Dhaka because of the coastal breeze.
March to May is hot and increasingly humid (30-35°C). Manageable but tiring.
June to October is the monsoon. Heavy rains, frequent flooding, and possible cyclones in the Bay of Bengal — particularly dangerous late in the season. Travel to Cox's Bazar and the Hill Tracts is awkward at best during the monsoon.
The Pohela Boishakh (Bengali New Year) on 14 April brings cultural events to DC Hill and elsewhere across the city. The Catholic feast of Christmas is celebrated with particular enthusiasm in the Firingi Bazar quarter.