Weather is probably a major factor when you plan your trip to Joetsu, 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 23°C, while the coldest months are February and January, with an average of 3°C. The rainiest months in Joetsu are December, July, January and September, with each month seeing an average of 251 mm of rainfall.