If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Cotonou: The hottest months are usually March and January with an average temp of 83°F, while the coldest months are August and July with an average of 79°F. The rainiest months in Cotonou are June, July, May, and September, with each month seeing an average of 9 inches of rainfall.