Weather is probably a major factor when you plan your trip to Harvey, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually July and August with an average temp of 66°F, while the coldest months are February and January with an average of 16°F. The snowiest months in Harvey are April, October, March, and December, with each month seeing an average of 9 inches of snowfall.