Interior weather by month
What a typical year looks like in Interior, South Dakota: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Interior 3 NE, 4 km from Interior; records cover 1949–2026.
The year at a glance
- Precipitation a year
- 19.6 in498 mm
- Snow a year
- 38 in97 cm
- Last spring freeze
- May 3
- First fall freeze
- Oct 4
- Heating degree days
- 6,332
- Cooling degree days
- 1,056
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are −10°−23° (heating, 99%) and 103°39° (cooling, 1%).
Month by month
Interior in January
Highs average 37°3° and lows 14°−10°, with 0.46 in12 mm of precipitation and 6 in14 cm of snow in a typical January.
- Record high
- 71°22° (2012)
- Record low
- −28°−33° (1963)
- Heating degree days
- 1220
- Cooling degree days
- 0
Interior in February
Highs average 41°5° and lows 16°−9°, with 0.55 in14 mm of precipitation and 6 in16 cm of snow in a typical February.
- Record high
- 75°24° (1962)
- Record low
- −31°−35° (1996)
- Heating degree days
- 1022
- Cooling degree days
- 0
Interior in March
Highs average 53°11° and lows 26°−3°, with 1.2 in29 mm of precipitation and 6 in15 cm of snow in a typical March.
- Record high
- 85°29° (1978)
- Record low
- −23°−31° (1960)
- Heating degree days
- 802
- Cooling degree days
- 0
Interior in April
Highs average 62°17° and lows 35°2°, with 2.3 in57 mm of precipitation and 6 in16 cm of snow in a typical April.
- Record high
- 94°34° (1980)
- Record low
- 3°−16° (1975)
- Heating degree days
- 501
- Cooling degree days
- 4
Interior in May
Highs average 72°22° and lows 46°8°, with 3.6 in92 mm of precipitation and 0.5 in1.3 cm of snow in a typical May.
- Record high
- 102°39° (1969)
- Record low
- 20°−7° (1967)
- Heating degree days
- 231
- Cooling degree days
- 42
Interior in June
Highs average 83°28° and lows 56°13°, with 3.5 in88 mm of precipitation in a typical June.
- Record high
- 109°43° (1988)
- Record low
- 32°0° (1998)
- Heating degree days
- 41
- Cooling degree days
- 167
Interior in July
Highs average 91°33° and lows 62°17°, with 2.2 in57 mm of precipitation in a typical July.
- Record high
- 115°46° (2026)
- Record low
- 42°6° (1971)
- Heating degree days
- 3
- Cooling degree days
- 367
Interior in August
Highs average 91°33° and lows 60°16°, with 1.8 in46 mm of precipitation in a typical August.
- Record high
- 111°44° (2026)
- Record low
- 35°2° (1978)
- Heating degree days
- 10
- Cooling degree days
- 331
Interior in September
Highs average 82°28° and lows 51°10°, with 1.4 in35 mm of precipitation in a typical September.
- Record high
- 106°41° (2001)
- Record low
- 25°−4° (1964)
- Heating degree days
- 97
- Cooling degree days
- 131
Interior in OctoberThis month
Highs average 65°19° and lows 38°3°, with 1.6 in40 mm of precipitation and 1.9 in4.8 cm of snow in a typical October.
- Record high
- 97°36° (1963)
- Record low
- 0°−18° (2020)
- Heating degree days
- 430
- Cooling degree days
- 14
Interior in November
Highs average 50°10° and lows 25°−4°, with 0.53 in13 mm of precipitation and 4 in9 cm of snow in a typical November.
- Record high
- 84°29° (1999)
- Record low
- −21°−29° (1959)
- Heating degree days
- 822
- Cooling degree days
- 0
Interior in December
Highs average 39°4° and lows 17°−9°, with 0.54 in14 mm of precipitation and 8 in20 cm of snow in a typical December.
- Record high
- 72°22° (1957)
- Record low
- −31°−35° (1983)
- Heating degree days
- 1153
- Cooling degree days
- 0