If you're looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Shirakawa: The hottest months are usually August and July, with an average temperature of 19°C, while the coldest months are January and February, with an average of -3°C. The rainiest months in Shirakawa are July, September, August and June, with each month seeing an average of 333 mm of rainfall.