You might spend a lot of your vacation inside, but if you want to see more of the area, looking at local weather trends is a good idea. The hottest months are usually July and August with an average temp of 65°F, while the coldest months are January and February with an average of 19°F. The snowiest months in Hayward are March, April, January, and February, with each month seeing an average of 9 inches of snowfall.