Planning for the weather is a good way to make your trip to Diamond Harbour relaxing and enjoyable, especially when you're splurging. The hottest months are usually April and May, with an average temperature of 30°C, while the coldest months are January and December, with an average of 23°C. The rainiest months in Diamond Harbour are August, July, September and June, with each month seeing an average of 377 mm of rainfall.