Planning for the weather is a good way to make your trip to Cerf Island relaxing and enjoyable, especially when you’re splurging. The hottest months are usually April and May with an average temp of 83°F, while the coldest months are July and August with an average of 80°F. The rainiest months in Cerf Island are January, December, May, and November, with each month seeing an average of 10 inches of rainfall.