Weather will likely play an important role when you plan your trip to Boston, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually September and August, with an average temperature of 26°C, while the coldest months are February and March, with an average of 25°C. The rainiest months in Boston are January, May, June and November, with each month seeing an average of 393 mm of rainfall.