Other facts from our historical weather data: When is summer in Yakima?The hottest season / summer takes place in June, July, August and September. Which is the warmest month in Yakima? July has an average maximum temperature of 32°C (90°F) and is the warmest month of the year. Which is the coldest month in Yakima? The coldest month is December with an average maximum temperature of 3°C (37°F). Which is the wettest month in Yakima? December tops the wettest month list with 37mm (1.5 in) of rainfall. Which is the driest month in Yakima? July is the driest month with 4mm (0.2 in) of precipitation. No idea where to travel to this year? We have a tool that recommends destinations based on your ideal conditions. Find out where to go with our weather planner.