Other facts from our historical weather data: Which is the warmest month in Nampa? July has an average maximum temperature of 21°C (70°F) and is the warmest month of the year. Which is the coldest month in Nampa? The coldest month is January with an average maximum temperature of -7°C (19°F). Which is the wettest month in Nampa? July tops the wettest month list with 86mm (3.4 in) of rainfall. Which is the driest month in Nampa? March is the driest month with 40mm (1.6 in) of precipitation. Which is the sunniest month in Nampa? June is the sunniest month with an average of 272 hours of sunshine. 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.