Weather is probably a major factor when you plan your trip to Grand-Lahou, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually March and April with an average temp of 82°F, while the coldest months are August and September with an average of 77°F. The rainiest months in Grand-Lahou are June, May, October, and July, with each month seeing an average of 9 inches of rainfall.