Taking into account the local weather in Filadelfia is an important factor for planning your visit, especially if you plan to spend your trip poolside. The hottest months are usually August and September with an average temp of 60°F, while the coldest months are January and December with an average of 59°F. The rainiest months in Filadelfia are May, April, October, and June, with each month seeing an average of 29 inches of rainfall.