Castlewood, South Dakota climate: Normal weather by month, frost dates and records
Castlewood's normal year runs from 3°F January nights to 83°F July afternoons, with 24.3 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 5.9°C, January lows of −16°C, July highs of 28°C, 618 mm of precipitation a year.
- NOAA stationCastlewood #2
- Station IDUSC00391520
- Location44.73°N 97.03°W
- Elevation1,689 ft (515 m)
- Population716
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Castlewood.
- Jan 22° 3°
- Feb 26° 6°
- Mar 39° 18°
- Apr 54° 30°
- May 67° 44°
- Jun 78° 54°
- Jul 83° 59°
- Aug 81° 56°
- Sep 72° 47°
- Oct 58° 34°
- Nov 41° 21°
- Dec 27° 9°
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 Castlewood each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 3°F. The most precipitation falls in June (3.97 in), the least in January (0.52 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 22°F | 3°F | 12.0°F | 0.52 | – | <1 | 31 | 9 h 10 min |
| February | 26°F | 6°F | 16.1°F | 0.58 | – | <1 | 28 | 10 h 20 min |
| March | 39°F | 18°F | 28.3°F | 1.12 | – | <1 | 27 | 11 h 50 min |
| April | 54°F | 30°F | 41.9°F | 2.13 | – | <1 | 19 | 13 h 30 min |
| May | 67°F | 44°F | 55.5°F | 3.18 | – | 1 | 3 | 14 h 50 min |
| June | 78°F | 54°F | 65.9°F | 3.97 | – | 2 | <1 | 15 h 30 min |
| July | 83°F | 59°F | 70.5°F | 3.49 | – | 5 | <1 | 15 h 20 min |
| August | 81°F | 56°F | 68.3°F | 3.08 | – | 3 | <1 | 14 h 10 min |
| September | 72°F | 47°F | 59.9°F | 2.69 | – | 1 | 1 | 12 h 40 min |
| October | 58°F | 34°F | 45.8°F | 2.28 | – | <1 | 15 | 11 h |
| November | 41°F | 21°F | 30.9°F | 0.76 | – | <1 | 27 | 9 h 40 min |
| December | 27°F | 9°F | 17.8°F | 0.53 | – | <1 | 31 | 8 h 50 min |
| Year (annual) | 54°F | 32°F | 42.7°F | 24.33 | – | 13 | 182 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −6°C | −16°C | −11.1°C | 13 mm |
| February | −3°C | −14°C | −8.8°C | 15 mm |
| March | 4°C | −8°C | −2.1°C | 28 mm |
| April | 12°C | −1°C | 5.5°C | 54 mm |
| May | 20°C | 6°C | 13.1°C | 81 mm |
| June | 25°C | 12°C | 18.8°C | 101 mm |
| July | 28°C | 15°C | 21.4°C | 89 mm |
| August | 27°C | 13°C | 20.2°C | 78 mm |
| September | 22°C | 8°C | 15.5°C | 68 mm |
| October | 14°C | 1°C | 7.7°C | 58 mm |
| November | 5°C | −6°C | −0.6°C | 19 mm |
| December | −3°C | −13°C | −7.9°C | 13 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Watertown (14 miles away), gets 41 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00391520; 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 Castlewood?
Normal highs sit between 65°F and 85°F in May, June, July, August and September.
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 USC00391520.
When is the last frost in Castlewood?
In Castlewood, the last spring frost (32°F) comes after May 6 in half of years and after May 20 in one year in ten; the first autumn frost comes before October 1 in half of years and before September 19 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 61 year in 10 after May 20; 9 in 10 after April 25
- First autumn frost, half of years before
- October 11 year in 10 before September 19; 9 in 10 before October 14
NOAA puts the median frost-free season at 145 days, and the season without a hard freeze (28°F) at 164 days.
A hard freeze (28°F) comes after April 29 in half of springs and before October 11 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Castlewood in zone 4a in ZIP code 57223, 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 USC00391520; 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 in Castlewood?
In a normal year in Castlewood, 13 days a year reach 90°F and 182 nights fall to 32°F or colder.
- Days at 90°F or more
- 13a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 182a normal year
- Days that stay below freezing
- 87high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USC00391520.
How sunny is Castlewood?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Castlewood, 4.1 kWh per square metre a day. July is the sunniest month (85%) and December the cloudiest (67%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 77% | 2.0 |
| February | 79% | 3.0 |
| March | 71% | 3.8 |
| April | 71% | 4.9 |
| May | 72% | 5.7 |
| June | 77% | 6.4 |
| July | 85% | 6.7 |
| August | 82% | 5.6 |
| September | 79% | 4.4 |
| October | 73% | 2.9 |
| November | 73% | 2.0 |
| December | 67% | 1.4 |
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 Castlewood need?
A normal year in Castlewood brings 8,568 heating degree days, 59% more than the median U.S. place (5,373), and 484 cooling degree days, 47% 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 2,344 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,642 | 0 |
| February | 1,370 | 0 |
| March | 1,140 | 1 |
| April | 695 | 1 |
| May | 316 | 20 |
| June | 65 | 91 |
| July | 18 | 188 |
| August | 38 | 140 |
| September | 197 | 43 |
| October | 599 | 2 |
| November | 1,025 | 0 |
| December | 1,463 | 0 |
| Year (annual) | 8,568 | 484 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00391520. 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.
Has Castlewood been warmer than normal lately?
2025 averaged 44.0°F, 1.3°F above the 1991-2020 normal of 42.7°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 44.5°F | +1.8°F | 24.92 |
| 2022 | 41.3°F | −1.4°F | 19.60 |
| 2023 | 43.4°F | +0.7°F | 24.94 |
| 2024 | 45.1°F | +2.4°F | 26.01 |
| 2025 | 44.0°F | +1.3°F | 33.69 |
Source: observed years: ACIS, station USC00391520. A year counts only with all twelve months complete.
How does Castlewood's climate compare?
Castlewood is warmer than 7 of the other 99 places with their own NOAA record in South Dakota, and wetter than 62. Across the 7,247 U.S. stations with normals, its annual mean of 42.7°F is warmer than 11%.
In the Köppen classification computed from these normals, Castlewood is Dfb: continental, no dry season, warm 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 Castlewood share this climate record?
6 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.
- Estelline, SD768 people · 12 mi SE
- Lake Norden, SD625 people · 14 mi SW
- Hayti, SD434 people · 10 mi SW
- Lake Poinsett, SD413 people · 11 mi S
- Claremont Colony, SD0 people · 4 mi E
- Poinsett Colony, SD0 people · 9 mi SE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Castlewood's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Castlewood. This page uses Castlewood #2; the other differs by site and elevation:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Castlewood station USC00391519 | in town | 1,685 ft | 41.7°F | 2°F | 81°F | 24.8 | – | May 10 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Castlewood's climate
What is the coldest month in Castlewood?
January, with a normal high of 22°F and a normal low of 3°F. The warmest is July (83°F by day, 59°F at night).
Does it snow in Castlewood?
Yes. NOAA publishes no 1991-2020 snowfall normal for Castlewood's NOAA station; the nearest record that keeps one, Watertown (14 miles away), records 41 inches of snow in a normal year.
What is the rainiest month in Castlewood?
June, with 3.97 in of precipitation in a normal year; the driest is January with 0.52 in.
What plant hardiness zone is Castlewood in?
The USDA's 2023 map puts Castlewood in zone 4a in ZIP code 57223, the nearest ZIP area.
How late can frost come in Castlewood?
In half of years the last 32°F night comes after May 6; in one year in ten it comes after May 20. Waiting until May 20 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
- Watertown, SD14 miles from this station, 43.0°F a year
- Clear Lake, SD17 miles from this station, 42.4°F a year
- Rauville (2 mi W), SD18 miles from this station, 42.7°F a year
- Arlington, SD26 miles from this station, 44.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made