Russia has over 2.5 million rivers; the largest are the Volga, Ob, Yenisei, Lena, Amur, Don and Kama. In summer the lowland rivers of European Russia and the south warm to +20…+24 °C and are suitable for swimming from June to August, while Siberian rivers stay cooler. River water temperature depends on length, depth, current and meltwater; we estimate it with a climate model. Values are computed for each riverside city separately, so upstream and downstream readings differ. Pick a river for temperature by city, a daily forecast and the monthly norm.