Roy Lake, South Dakota climate: Climate normals at a NOAA weather station
Roy Lake's normal year runs from 3°F January nights to 82°F July afternoons, with 25.0 inches of precipitation and 48 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.4°C, January lows of −16°C, July highs of 28°C, 635 mm of precipitation a year.
- NOAA stationRoy Lake
- Station IDUSC00397326
- Location45.71°N 97.43°W
- Elevation1,810 ft (552 m)
On October 22, the normal high in Roy Lake is 54°F and the normal low 35°F, and the chance of measurable rain or snow is 21%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Roy Lake.
- Jan 22° 3°
- Feb 26° 5°
- Mar 38° 18°
- Apr 53° 32°
- May 67° 46°
- Jun 76° 58°
- Jul 82° 62°
- Aug 81° 60°
- Sep 72° 51°
- Oct 57° 37°
- Nov 40° 23°
- Dec 27° 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 at Roy Lake each month?
July is the warmest month, with normal highs of 82°F; January the coldest, with normal lows of 3°F. The most precipitation falls in July (4.41 in), the least in January (0.55 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 22°F | 3°F | 12.1°F | 0.55 | 6.6 | 5 | <1 | 31 | 9 h |
| February | 26°F | 5°F | 15.4°F | 0.63 | 9.2 | 5 | <1 | 28 | 10 h 20 min |
| March | 38°F | 18°F | 27.7°F | 0.98 | 7.0 | 5 | <1 | 29 | 11 h 50 min |
| April | 53°F | 32°F | 42.4°F | 2.06 | 7.2 | 7 | <1 | 16 | 13 h 30 min |
| May | 67°F | 46°F | 56.4°F | 3.15 | 0.2 | 11 | <1 | 3 | 14 h 50 min |
| June | 76°F | 58°F | 67.1°F | 4.27 | 0.0 | 11 | <1 | <1 | 15 h 40 min |
| July | 82°F | 62°F | 72.0°F | 4.41 | 0.0 | 9 | 2 | <1 | 15 h 20 min |
| August | 81°F | 60°F | 70.3°F | 2.62 | 0.0 | 8 | 1 | <1 | 14 h 10 min |
| September | 72°F | 51°F | 61.3°F | 2.50 | 0.0 | 8 | <1 | 1 | 12 h 40 min |
| October | 57°F | 37°F | 47.1°F | 2.21 | 2.5 | 7 | <1 | 11 | 11 h |
| November | 40°F | 23°F | 31.5°F | 0.85 | 4.3 | 4 | <1 | 25 | 9 h 30 min |
| December | 27°F | 10°F | 18.4°F | 0.76 | 11.1 | 6 | <1 | 31 | 8 h 40 min |
| Year (annual) | 53°F | 34°F | 43.5°F | 24.99 | 48.1 | 84 | 4 | 174 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −6°C | −16°C | −11.1°C | 14 mm | 17 cm |
| February | −4°C | −15°C | −9.2°C | 16 mm | 23 cm |
| March | 3°C | −8°C | −2.4°C | 25 mm | 18 cm |
| April | 12°C | 0°C | 5.8°C | 52 mm | 18 cm |
| May | 19°C | 8°C | 13.6°C | 80 mm | 1 cm |
| June | 25°C | 14°C | 19.5°C | 108 mm | 0 cm |
| July | 28°C | 17°C | 22.2°C | 112 mm | 0 cm |
| August | 27°C | 16°C | 21.3°C | 67 mm | 0 cm |
| September | 22°C | 11°C | 16.3°C | 64 mm | 0 cm |
| October | 14°C | 3°C | 8.4°C | 56 mm | 6 cm |
| November | 5°C | −5°C | −0.3°C | 22 mm | 11 cm |
| December | −3°C | −12°C | −7.6°C | 19 mm | 28 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00397326; 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.
Which months are mildest at Roy Lake?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, September has the fewest days with rain (8).
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 USC00397326.
When is the last frost at Roy Lake?
In Roy Lake, the last spring frost (32°F) comes after May 2 in half of years and after May 15 in one year in ten; the first autumn frost comes before October 9 in half of years and before September 27 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 21 year in 10 after May 15; 9 in 10 after April 19
- First autumn frost, half of years before
- October 91 year in 10 before September 27; 9 in 10 before October 22
NOAA puts the median frost-free season at 160 days, and the season without a hard freeze (28°F) at 178 days.
A hard freeze (28°F) comes after April 24 in half of springs and before October 20 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Roy Lake in zone 4a in ZIP code 57247, the nearest ZIP area.
Frost dates for every NOAA station in South Dakota · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00397326; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 at Roy Lake?
In a normal year in Roy Lake, 4 days a year reach 90°F, 174 nights fall to 32°F or colder and 84 days bring measurable precipitation.
- Days at 90°F or more
- 4a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 174a normal year
- Days that stay below freezing
- 91high of 32°F or less
- Days with 0.01 inch of precipitation
- 84a normal year
- Days with 1 inch of snow or more
- 18a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USC00397326.
How sunny is it at Roy Lake?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds at Roy Lake, 4.0 kWh per square metre a day. July is the sunniest month (83%) and December the cloudiest (65%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 78% | 1.9 |
| February | 82% | 3.0 |
| March | 73% | 3.9 |
| April | 72% | 4.9 |
| May | 71% | 5.6 |
| June | 76% | 6.3 |
| July | 83% | 6.6 |
| August | 81% | 5.5 |
| September | 78% | 4.2 |
| October | 70% | 2.7 |
| November | 70% | 1.8 |
| December | 65% | 1.3 |
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 many heating and cooling degree days does Roy Lake record?
A normal year at Roy Lake brings 8,417 heating degree days, 57% more than the median U.S. place (5,373), and 619 cooling degree days, 32% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,541 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,640 | 0 |
| February | 1,389 | 0 |
| March | 1,156 | 0 |
| April | 677 | 0 |
| May | 291 | 24 |
| June | 59 | 120 |
| July | 12 | 229 |
| August | 19 | 185 |
| September | 167 | 58 |
| October | 560 | 4 |
| November | 1,004 | 0 |
| December | 1,445 | 0 |
| Year (annual) | 8,417 | 619 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00397326. 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 Roy Lake's climate compare?
Roy Lake is warmer than 18 of the 100 places with their own NOAA record in South Dakota, and wetter than 66. Across the 7,247 U.S. stations with normals, its annual mean of 43.5°F is warmer than 14%.
In the Köppen classification computed from these normals, Roy Lake 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.
Which places near Roy Lake share this climate record?
3 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Eden, SD91 people · 6 mi S
- Lake City, SD45 people · 1 mi NE
- Clear Lake, SD30 people · 4 mi E
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Roy Lake's climate
What is the coldest month at Roy Lake?
January, with a normal high of 22°F and a normal low of 3°F. The warmest is July (82°F by day, 62°F at night).
Does it snow at Roy Lake?
Yes: 48 inches in a normal year, falling on 24 days with 0.1 inch or more, the most in December (11.1 inches).
What is the rainiest month at Roy Lake?
July, with 4.41 in of precipitation in a normal year; the driest is January with 0.55 in.
What plant hardiness zone is Roy Lake in?
The USDA's 2023 map puts Roy Lake in zone 4a in ZIP code 57247, the nearest ZIP area.
How late can frost come at Roy Lake?
In half of years the last 32°F night comes after May 2; in one year in ten it comes after May 15. Waiting until May 15 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
- Britton, SD16 miles from this station, 42.3°F a year
- Waubay, SD21 miles from this station, 44.1°F a year
- Sisseton, SD22 miles from this station, 44.0°F a year
- Forman, ND24 miles from this station, 41.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made