Kolkata has a tropic wet and dry climate and the best time to visit the city is from October to March.
(March-May) is the hottest season with maximum temperature crossing 40°C and minimum above 30°C. This is not the best time for visiting as scorching sun makes it difficult to travel outdoors.
(November to February) enjoys a cool climate with temperature hovering around 9°C to 18°C. This is a good time to visit Kolkata as the weather is cool and occasional rainfall makes the evening very pleasant.
(June to September) provide a major portion of annual rainfall and heavy showers are occurring during this season. Though the weather is cool but humidity rises. This is also the time for a major celebration in Kolkata, Kali Pooja (Dussera festival) spreading across 9 days festivities and religious functions in October. This has been celebrated with much enthusiasm and fervor.
Kolkata is a beautiful cultural city which is best visited during the post monsoons and winter months. While summers are hot and comfortable the monsoons are humid. Winter in Kolkata is mild and is a good time for enjoying outdoor travel.