Weather is probably a major factor when you plan your trip to San Jose, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually April and May with an average temp of 83°F, while the coldest months are January and February with an average of 78°F. The rainiest months in San Jose are July, September, August, and June, with each month seeing an average of 13 inches of rainfall.