Cambodia has a hot and humid climate. The weather in Kampot, however, is a bit cooler because of its nearness to the oceans and the mountains. The average temperature of the province is around 27º Celsius.
The best time to visit Kampot is from November to February, when it is coolest. The range of temperature around this time would be from below 20º to below 30º Celsius. It is hottest there during summer in March to June, with temperatures sometimes reaching 38º Celsius.
There is abundant rainfall during rainy season in Kampot, from June to October. However, the rains only fall in the afternoon and just last a couple of hours. It could still be a good time to visit as there are fewer tourists around, and the air becomes cooler and fresher after the rains. Be prepared, though, for mud and even landslides outside the town.