Weather is probably a major factor when you plan your trip to Toshima, and keep 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 temp of 80°F, while the coldest months are January and February with an average of 60°F. The rainiest months in Toshima are June, July, September, and May, with each month seeing an average of 15 inches of rainfall.