If you are planning to visit Dervan in order to attend the annual celebration of Shree Shivaraya birth anniversary, then it is best to visit in during spring.
The summer months are hot and humid. They usually extend from April to June. During this time, the climate may not be very comfortable outdoorsy activities. Sightseeing can get very uncomfortable because of the sultry weather.
The winters are very comfortable, although the temperature does not drop much because of the tropical location. However, the weather is much pleasant and suitable for exploration.
However, the beauty of this region can be best experienced during the monsoons, so between June and October, one may come and experience the enticing rainfall of the Western Ghats.