Rasht is one of Iran's wettest cities, and that is not a footnote - it shapes the place. Spring and autumn are the most comfortable seasons, with green countryside, milder temperatures, and fewer of the hot, humid days that can make summer heavy.
Summer is lively because Iranian families head north for the Caspian, but expect humidity and crowded roads. Winter is cool, grey, and rainy rather than harsh. Bring a rain jacket almost any time of year; locals do not call this a rainy city for nothing.