Weather is probably a major factor when you plan your trip to Kusatsu, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and July, with an average temperature of 24°C, while the coldest months are January and February, with an average of 5°C. The rainiest months in Kusatsu are July, June, September and August, with each month seeing an average of 203 mm of rainfall.