If you’re hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Nanao: The hottest months are usually August and July, with an average temperature of 24°C, while the coldest months are February and January, with an average of 5°C. The rainiest months in Nanao are July, September, August and December, with each month seeing an average of 260 mm of rainfall.