Weather is only one factor, but it can really affect your travel plans, especially if you're planning an extended stay in Sunnyside. The hottest months are usually July and August with an average temp of 69°F, while the coldest months are January and December with an average of 27°F. The snowiest months in Sunnyside are February, March, January, and November, with each month seeing an average of 5 inches of snowfall.