Lyman County Climate
Lyman County, South Dakota
Avg Annual Temp
46.9°F
Annual Precip
20.2"
Annual Snowfall
39.6"
Extreme Heat Days
36.46666666666667
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Lyman County Weather
Warmer and Drier Than the National Average
Lyman County averages 46.9°F annually, placing it well below the national median temperature but higher than many northern peers. The local climate is characterized by low annual precipitation of just 20.2 inches. This creates a semi-arid environment with intense summer exposure.
Outpacing the State in Summer Heat
With an annual average of 46.9°F, Lyman is warmer than the South Dakota state average of 45.6°F. It records a staggering 36 days of extreme heat over 90°F, more than double the count of many eastern counties. Meanwhile, its precipitation levels trail the state average by over two inches.
Central South Dakota's Heat Hub
Lyman County stands out for its high volume of extreme heat days compared to the more moderate eastern counties. Its 39.6 inches of snowfall is significant, even as its total annual precipitation remains a low 20.2 inches. This combination of dry air and heavy winter accumulation creates a rugged climate profile.
Intense Summers and Snowy Winters
July averages reach 74.2°F, fueled by 36 days of extreme heat that push the local climate to its limits. Winter brings a sharp contrast, with a December-to-February average of 21.8°F and nearly 40 inches of snow. These extremes require residents to prepare for both heat waves and heavy drifts.
Managing High Heat and Heavy Snow
Central air conditioning is a necessity in Lyman County to navigate the 36 days of temperatures above 90°F. Reliable winter vehicles are also a must, as the county sees nearly 40 inches of snow and January lows of 19.6°F. Water conservation is often important given the low 20.2-inch annual precipitation total.
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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.