The Bengal coast has a sharp seasonal rhythm. October to February is the best window — dry, cool, with daytime temperatures in the mid-20s and the sea calm enough for swimming. Christmas week and Bengali New Year (mid-April) are the busiest of the year and rooms are scarce; book ahead.
March to early May is hot and sticky but the sea is at its calmest. Mid-June to September is monsoon — wind, big surf, periodic tropical storms making landfall, no fishing boats out, and many resorts effectively closed. Beautiful in its own way but not for swimming.