If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Tonawanda: The hottest months are usually July and August with an average temp of 68°F, while the coldest months are February and January with an average of 30°F. The snowiest months in Tonawanda are January, February, March, and December, with each month seeing an average of 15 inches of snowfall.