Other facts from our historical weather data: Which is the warmest month in San Isidro? April has an average maximum temperature of 25°C (77°F) and is the warmest month of the year. Which is the coldest month in San Isidro? The coldest month is January with an average maximum temperature of 23°C (73°F). Which is the wettest month in San Isidro? October tops the wettest month list with 737mm (29 in) of rainfall. Which is the driest month in San Isidro? February is the driest month with 104mm (4.1 in) of precipitation. Which is the sunniest month in San Isidro? March is the sunniest month with an average of 270 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.