Other facts from our historical weather data: When is the rainy season in Chiang Saen? Rainy season in Chiang Saen occurs in the months of May, June, July, August and September. Which is the hottest month in Chiang Saen? April has an average maximum temperature of 36°C (97°F) and is the hottest month of the year. Which is the coolest month in Chiang Saen? The coolest month is January with an average maximum temperature of 28°C (82°F). Which is the wettest month in Chiang Saen? August tops the wettest month list with 397mm (15.6 in) of rainfall. Which is the driest month in Chiang Saen? February is the driest month with 14mm (0.6 in) of precipitation. Which is the sunniest month in Chiang Saen? March is the sunniest month with an average of 295 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.