If you’re hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in San Jose City: The hottest months are usually April and May, with an average temperature of 27°C, while the coldest months are January and February, with an average of 25°C. The rainiest months in San Jose City are July, August, September and June, with each month seeing an average of 398 mm of rainfall.