Taking into account the local weather in Lower Grand Lagoon is an important factor for planning your visit, especially if you plan to spend your trip poolside. The hottest months are usually August and July with an average temp of 81°F, while the coldest months are January and February with an average of 58°F. The rainiest months in Lower Grand Lagoon are August, July, September, and June, with each month seeing an average of 7 inches of rainfall.