If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Shiojiri: 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 -1°C. The rainiest months in Shiojiri are July, October, September and June, with each month seeing an average of 178 mm of rainfall.