Planning for the weather is an important factor for making your trip to Yosemite National Park a success, especially when you're splurging. The hottest months are usually July and August with an average temp of 58°F, while the coldest months are February and December with an average of 27°F. The rainiest months in Yosemite National Park are December, January, March, and February, with each month seeing an average of 8 inches of rainfall.