Planning for the weather is a good way to make your trip to Saint-Denis relaxing and enjoyable, especially when you're splurging. The hottest months are usually February and January with an average temp of 78°F, while the coldest months are August and July with an average of 70°F. The rainiest months in Saint-Denis are January, February, March, and December, with each month seeing an average of 11 inches of rainfall.