Stephan, South Dakota climate: Normal weather by month, frost dates and records
Stephan's normal year runs from 5°F January nights to 85°F July afternoons, with 21.2 inches of precipitation and 37 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.0°C, January lows of −15°C, July highs of 30°C, 538 mm of precipitation a year.
- NOAA stationStephan (2 mi NW)
- Station IDUSC00397992
- Location44.27°N 99.44°W
- Elevation1,805 ft (550 m)
- From the center1 miles
- Population (census place)7
On October 23, the normal high in Stephan is 56°F and the normal low 30°F, and the chance of measurable rain or snow is 17%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Stephan.
- Jan 26° 5°
- Feb 31° 8°
- Mar 44° 19°
- Apr 57° 31°
- May 68° 43°
- Jun 79° 54°
- Jul 85° 60°
- Aug 84° 58°
- Sep 76° 47°
- Oct 60° 33°
- Nov 44° 20°
- Dec 31° 10°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Stephan each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 5°F. The most precipitation falls in June (3.80 in), the least in January (0.47 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 26°F | 5°F | 15.4°F | 0.47 | 6.0 | 4 | <1 | 31 | 9 h 10 min |
| February | 31°F | 8°F | 19.5°F | 0.66 | 9.3 | 4 | <1 | 27 | 10 h 30 min |
| March | 44°F | 19°F | 31.3°F | 0.98 | 6.5 | 4 | <1 | 27 | 11 h 50 min |
| April | 57°F | 31°F | 43.8°F | 1.95 | 4.4 | 7 | <1 | 16 | 13 h 20 min |
| May | 68°F | 43°F | 55.8°F | 3.18 | 0.0 | 9 | 1 | 4 | 14 h 40 min |
| June | 79°F | 54°F | 66.2°F | 3.80 | 0.0 | 10 | 2 | <1 | 15 h 30 min |
| July | 85°F | 60°F | 72.4°F | 2.89 | 0.0 | 7 | 10 | <1 | 15 h 10 min |
| August | 84°F | 58°F | 70.7°F | 2.17 | 0.0 | 6 | 9 | <1 | 14 h |
| September | 76°F | 47°F | 61.7°F | 1.95 | 0.0 | 6 | 4 | 2 | 12 h 40 min |
| October | 60°F | 33°F | 46.6°F | 1.89 | 1.1 | 6 | <1 | 13 | 11 h |
| November | 44°F | 20°F | 31.8°F | 0.63 | 5.0 | 3 | <1 | 27 | 9 h 40 min |
| December | 31°F | 10°F | 20.1°F | 0.60 | 4.3 | 4 | <1 | 31 | 8 h 50 min |
| Year (annual) | 57°F | 32°F | 44.6°F | 21.17 | 36.6 | 71 | 26 | 179 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −3°C | −15°C | −9.2°C | 12 mm | 15 cm |
| February | −1°C | −13°C | −6.9°C | 17 mm | 24 cm |
| March | 7°C | −7°C | −0.4°C | 25 mm | 17 cm |
| April | 14°C | −1°C | 6.6°C | 50 mm | 11 cm |
| May | 20°C | 6°C | 13.2°C | 81 mm | 0 cm |
| June | 26°C | 12°C | 19.0°C | 97 mm | 0 cm |
| July | 30°C | 15°C | 22.4°C | 73 mm | 0 cm |
| August | 29°C | 14°C | 21.5°C | 55 mm | 0 cm |
| September | 24°C | 8°C | 16.5°C | 50 mm | 0 cm |
| October | 16°C | 1°C | 8.1°C | 48 mm | 3 cm |
| November | 7°C | −7°C | −0.1°C | 16 mm | 13 cm |
| December | −1°C | −12°C | −6.6°C | 15 mm | 11 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00397992; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Stephan?
Normal highs sit between 65°F and 85°F in May, June, August and September. Of those, September has the fewest days with rain (6).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00397992.
When is the last frost in Stephan?
In Stephan, the last spring frost (32°F) comes after May 10 in half of years and after May 24 in one year in ten; the first autumn frost comes before September 29 in half of years and before September 16 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- May 101 year in 10 after May 24; 9 in 10 after April 29
- First autumn frost, half of years before
- September 291 year in 10 before September 16; 9 in 10 before October 11
NOAA puts the median frost-free season at 140 days, and the season without a hard freeze (28°F) at 158 days.
A hard freeze (28°F) comes after May 2 in half of springs and before October 6 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Stephan in zone 4b in ZIP code 57346. By the map's own method, the average of each year's coldest night over 1991-2020, Stephan's NOAA station is in zone 4b: the coldest night of a typical year reaches −21°F (18 complete years).
Frost dates for every NOAA station in South Dakota · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00397992; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Stephan?
In a normal year in Stephan, 26 days a year reach 90°F (3 of them 100°F or more), 179 nights fall to 32°F or colder and 71 days bring measurable precipitation.
- Days at 90°F or more
- 26a normal year
- Days at 100°F or more
- 3a normal year
- Nights at 32°F or colder
- 179a normal year
- Days that stay below freezing
- 62high of 32°F or less
- Days with 0.01 inch of precipitation
- 71a normal year
- Days with 1 inch of snow or more
- 10a normal year
The highest temperature in this station's record (since 1903) is 112°F, on August 13, 1965; the lowest is −43°F, on January 12, 1912.
The wettest calendar year on that record is 1996, with 29.46 in; the snowiest season is 1985–86, with 89.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00397992; records: ACIS (NOAA Regional Climate Centers), station USC00397992. Records use complete months only; a month missing more than three days is left out.
How sunny is Stephan?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Stephan, 4.2 kWh per square metre a day. July is the sunniest month (86%) and December the cloudiest (71%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 78% | 2.0 |
| February | 79% | 3.0 |
| March | 72% | 3.9 |
| April | 72% | 5.0 |
| May | 74% | 5.9 |
| June | 80% | 6.7 |
| July | 86% | 6.9 |
| August | 83% | 5.7 |
| September | 81% | 4.5 |
| October | 74% | 3.0 |
| November | 74% | 2.0 |
| December | 71% | 1.5 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Stephan need?
A normal year in Stephan brings 8,031 heating degree days, 49% more than the median U.S. place (5,373), and 642 cooling degree days, 29% fewer than the median (908). Eight months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,558 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,536 | 0 |
| February | 1,274 | 0 |
| March | 1,045 | 0 |
| April | 638 | 1 |
| May | 303 | 18 |
| June | 70 | 108 |
| July | 13 | 244 |
| August | 24 | 201 |
| September | 167 | 68 |
| October | 573 | 3 |
| November | 996 | 0 |
| December | 1,392 | 0 |
| Year (annual) | 8,031 | 642 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00397992. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
How does Stephan's climate compare?
Stephan is warmer than 35 of the other 99 places with their own NOAA record in South Dakota, and wetter than 36. Across the 7,247 U.S. stations with normals, its annual mean of 44.6°F is warmer than 18%.
In the Köppen classification computed from these normals, Stephan is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Questions about Stephan's climate
What is the coldest month in Stephan?
January, with a normal high of 26°F and a normal low of 5°F. The warmest is July (85°F by day, 60°F at night).
Does it snow in Stephan?
Yes: 37 inches in a normal year, falling on 14 days with 0.1 inch or more, the most in February (9.3 inches).
What is the rainiest month in Stephan?
June, with 3.80 in of precipitation in a normal year; the driest is January with 0.47 in.
What plant hardiness zone is Stephan in?
The USDA's 2023 map puts Stephan in zone 4b in ZIP code 57346. By the same method at Stephan's NOAA station, the coldest night of a typical year reaches −21°F (18 years, 1991-2020): zone 4b.
How late can frost come in Stephan?
In half of years the last 32°F night comes after May 10; in one year in ten it comes after May 24. Waiting until May 24 leaves about a one-in-ten chance of a later frost.
Nearby and next
- South Dakota climateThe statewide normals and every place in the state
- Lake Sharpe Project, SD14 miles from this station, 46.7°F a year
- Highmore, SD17 miles from this station, 45.8°F a year
- Harrold (12 mi SSW), SD19 miles from this station, 44.3°F a year
- Gann Valley, SD27 miles from this station, 45.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made