Weather will likely play an important role when you plan your trip to Federal Way, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and July with an average temp of 64°F, while the coldest months are February and December with an average of 40°F. The rainiest months in Federal Way are November, December, January, and March, with each month seeing an average of 8 inches of rainfall.