Temperature for May
In Watertown, SD during May the average high temperature is 69.1°F. The hottest day on record was May 10, 1948 when the temperature hit 120.2°F.

In Watertown, SD during May the average high temperature is 69.1°F. The hottest day on record was May 10, 1948 when the temperature hit 120.2°F.
In May the average monthly rainfall in Watertown, SD is 2.02 inches with rain usually falling on between 10 and 11 days. 1949 was the driest May with only 0.00 inches of rain falling, and 1996 was the wettest May with 5.25 inches of rain. The wettest single day in May was 8 May 1978 when 1.69 inches of rain fell.
In May it usually snows on between 0 and 1 days. There are thunderstorms on between 2 and 3 days in May.