If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Beaverton: The hottest months are usually August and July with an average temp of 66°F, while the coldest months are February and December with an average of 42°F. The rainiest months in Beaverton are December, January, November, and March, with each month seeing an average of 7 inches of rainfall.