Taking into account the local weather in Formosa is an important factor for planning your visit, especially if you plan to spend your trip poolside. The hottest months are usually January and February with an average temp of 81°F, while the coldest months are July and June with an average of 64°F. The rainiest months in Formosa are November, October, December, and April, with each month seeing an average of 7 inches of rainfall.