Other facts from our historical weather data: Which is the warmest month in Alta? July has an average maximum temperature of 17°C (63°F) and is the warmest month of the year. Which is the coldest month in Alta? The coldest month is January with an average maximum temperature of -6°C (21°F). Which is the wettest month in Alta? July tops the wettest month list with 85mm (3.3 in) of rainfall. Which is the driest month in Alta? March is the driest month with 45mm (1.8 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.