Mellette County Climate
Mellette County, South Dakota
Avg Annual Temp
48.1°F
Annual Precip
20.4"
Annual Snowfall
45.1"
Extreme Heat Days
39.25
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Mellette County Weather
One of the Region's Warmest Spots
Mellette County averages 48.1°F annually, which is notably warmer than its South Dakota peers. However, it remains below the national median temperature due to its northern latitude. The local climate is marked by significant extreme heat and moderate total precipitation.
A State Leader in Extreme Heat
With 39 days of extreme heat over 90°F, Mellette County is much hotter in the summer than the South Dakota average. Its annual temperature of 48.1°F is also well above the state average of 45.6°F. Precipitation levels are slightly lower than the state norm, totaling 20.4 inches.
Topping the Region in Snow and Sun
Mellette County is an outlier with its high count of 39 heat days and its significant 45.1 inches of snowfall. It experiences more extreme heat than almost all its neighbors while maintaining heavy winter totals. This volatility makes it one of the more climate-stressed counties in the state.
Intense Summer Sun and Snowy Winters
Summer in Mellette is hot, with a July average of 74.7°F and over five weeks of 90°F days. Winters are equally intense, averaging 25.0°F from December to February with over 45 inches of snow. The transition from intense heat to heavy snow requires significant resilience from local infrastructure.
Resilience Against Heat and Drifts
Robust air conditioning is critical to handle the 39 days of extreme heat each summer. Simultaneously, residents need high-performance winter gear to manage 45.1 inches of snow and January lows of 23.1°F. Home maintenance should focus on both heat reflection and heavy-duty winter insulation.
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Data source: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020.
Climate normals are 30-year averages of weather variables computed from 1991 to 2020. Station data is aggregated to county level using spatial averaging. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.