Fort Thompson weather by month
What a typical year looks like in Fort Thompson, South Dakota: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Lake Sharpe Project, 5 km from Fort Thompson; records cover 1965–2026.
The year at a glance
- Precipitation a year
- 20.1 in511 mm
- Snow a year
- 19 in48 cm
- Last spring freeze
- May 6
- First fall freeze
- Oct 7
- Heating degree days
- 7,441
- Cooling degree days
- 802
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are −15°−26° (heating, 99%) and 100°38° (cooling, 1%).
Month by month
Fort Thompson in January
Highs average 29°−1° and lows 7°−14°, with 0.48 in12 mm of precipitation and 2.7 in6.9 cm of snow in a typical January.
- Record high
- 65°18° (1981)
- Record low
- −31°−35° (1970)
- Heating degree days
- 1452
- Cooling degree days
- 0
Fort Thompson in February
Highs average 35°2° and lows 10°−12°, with 0.54 in14 mm of precipitation and 5 in14 cm of snow in a typical February.
- Record high
- 72°22° (2000)
- Record low
- −37°−38° (1994)
- Heating degree days
- 1201
- Cooling degree days
- 0
Fort Thompson in March
Highs average 46°8° and lows 20°−6°, with 0.92 in23 mm of precipitation and 3 in8 cm of snow in a typical March.
- Record high
- 87°31° (2026)
- Record low
- −21°−29° (1996)
- Heating degree days
- 988
- Cooling degree days
- 0
Fort Thompson in April
Highs average 59°15° and lows 31°0°, with 1.8 in45 mm of precipitation and 2.6 in6.6 cm of snow in a typical April.
- Record high
- 96°36° (1980)
- Record low
- 4°−16° (1975)
- Heating degree days
- 596
- Cooling degree days
- 1
Fort Thompson in May
Highs average 71°21° and lows 44°7°, with 3.2 in80 mm of precipitation in a typical May.
- Record high
- 97°36° (2004)
- Record low
- 21°−6° (2005)
- Heating degree days
- 259
- Cooling degree days
- 26
Fort Thompson in June
Highs average 80°27° and lows 55°13°, with 3.8 in97 mm of precipitation in a typical June.
- Record high
- 110°43° (1988)
- Record low
- 34°1° (1998)
- Heating degree days
- 50
- Cooling degree days
- 134
Fort Thompson in July
Highs average 88°31° and lows 61°16°, with 2.8 in71 mm of precipitation in a typical July.
- Record high
- 112°44° (2006)
- Record low
- 40°4° (1971)
- Heating degree days
- 7
- Cooling degree days
- 297
Fort Thompson in August
Highs average 86°30° and lows 59°15°, with 2.2 in56 mm of precipitation in a typical August.
- Record high
- 110°43° (1965)
- Record low
- 41°5° (1974)
- Heating degree days
- 13
- Cooling degree days
- 250
Fort Thompson in September
Highs average 78°26° and lows 50°10°, with 2 in51 mm of precipitation in a typical September.
- Record high
- 104°40° (2002)
- Record low
- 24°−4° (1974)
- Heating degree days
- 124
- Cooling degree days
- 89
Fort Thompson in OctoberThis month
Highs average 62°17° and lows 36°2°, with 1.6 in41 mm of precipitation and 0.1 in0.3 cm of snow in a typical October.
- Record high
- 96°36° (2015)
- Record low
- 6°−14° (2020)
- Heating degree days
- 507
- Cooling degree days
- 5
Fort Thompson in November
Highs average 46°8° and lows 23°−5°, with 0.43 in11 mm of precipitation and 1.2 in3 cm of snow in a typical November.
- Record high
- 85°29° (1999)
- Record low
- −8°−22° (1985)
- Heating degree days
- 916
- Cooling degree days
- 0
Fort Thompson in December
Highs average 34°1° and lows 11°−12°, with 0.35 in8.9 mm of precipitation and 4 in10 cm of snow in a typical December.
- Record high
- 69°21° (1998)
- Record low
- −29°−34° (1990)
- Heating degree days
- 1328
- Cooling degree days
- 0