Castle Valley, Utah climate: Normal weather by month, frost dates and records
Castle Valley's normal year runs from 18°F January nights to 95°F July afternoons, with 12.3 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 12.6°C, January lows of −8°C, July highs of 35°C, 313 mm of precipitation a year.
- NOAA stationCastle Valley (1 mi SE)
- Station IDUSC00421240
- Location38.62°N 109.39°W
- Elevation4,905 ft (1,495 m)
- Population367
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Castle Valley.
- Jan 39° 18°
- Feb 46° 25°
- Mar 58° 33°
- Apr 66° 41°
- May 77° 50°
- Jun 89° 61°
- Jul 95° 68°
- Aug 92° 65°
- Sep 83° 56°
- Oct 68° 42°
- Nov 52° 30°
- Dec 39° 19°
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 Castle Valley each month?
July is the warmest month, with normal highs of 95°F; January the coldest, with normal lows of 18°F. The most precipitation falls in October (1.48 in), the least in June (0.59 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 39°F | 18°F | 28.4°F | 0.95 | – | <1 | 30 | 9 h 40 min |
| February | 46°F | 25°F | 35.7°F | 1.06 | – | <1 | 23 | 10 h 40 min |
| March | 58°F | 33°F | 45.8°F | 1.11 | – | <1 | 9 | 11 h 50 min |
| April | 66°F | 41°F | 53.2°F | 0.81 | – | <1 | 4 | 13 h 10 min |
| May | 77°F | 50°F | 63.3°F | 0.88 | – | 1 | <1 | 14 h 10 min |
| June | 89°F | 61°F | 74.9°F | 0.59 | – | 20 | <1 | 14 h 50 min |
| July | 95°F | 68°F | 81.5°F | 0.97 | – | 27 | <1 | 14 h 40 min |
| August | 92°F | 65°F | 78.6°F | 1.06 | – | 27 | <1 | 13 h 40 min |
| September | 83°F | 56°F | 69.7°F | 1.31 | – | 9 | <1 | 12 h 30 min |
| October | 68°F | 42°F | 54.9°F | 1.48 | – | <1 | 4 | 11 h 20 min |
| November | 52°F | 30°F | 41.0°F | 1.11 | – | <1 | 18 | 10 h 10 min |
| December | 39°F | 19°F | 29.2°F | 1.01 | – | <1 | 31 | 9 h 30 min |
| Year (annual) | 67°F | 42°F | 54.7°F | 12.34 | – | 84 | 118 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 4°C | −8°C | −2.0°C | 24 mm |
| February | 8°C | −4°C | 2.1°C | 27 mm |
| March | 15°C | 1°C | 7.7°C | 28 mm |
| April | 19°C | 5°C | 11.8°C | 21 mm |
| May | 25°C | 10°C | 17.4°C | 22 mm |
| June | 32°C | 16°C | 23.8°C | 15 mm |
| July | 35°C | 20°C | 27.5°C | 25 mm |
| August | 34°C | 18°C | 25.9°C | 27 mm |
| September | 29°C | 13°C | 20.9°C | 33 mm |
| October | 20°C | 5°C | 12.7°C | 38 mm |
| November | 11°C | −1°C | 5.0°C | 28 mm |
| December | 4°C | −7°C | −1.6°C | 26 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. Castle Valley's own co-op station Castle Valley station does: 15 inches of snow in a normal year (see the other stations below).
Source: NOAA NCEI 1991-2020 monthly normals, station USC00421240; 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 Castle Valley?
Normal highs sit between 65°F and 85°F in April, May, September and October.
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 USC00421240.
When is the last frost in Castle Valley?
In Castle Valley, the last spring frost (32°F) comes after April 19 in half of years and after May 3 in one year in ten; the first autumn frost comes before October 21 in half of years and before October 8 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
- April 191 year in 10 after May 3; 9 in 10 after April 4
- First autumn frost, half of years before
- October 211 year in 10 before October 8; 9 in 10 before November 4
NOAA puts the median frost-free season at 184 days, and the season without a hard freeze (28°F) at 210 days.
A hard freeze (28°F) comes after April 4 in half of springs and before October 30 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Castle Valley in zone 7a in ZIP code 84532, the nearest ZIP area.
Frost dates for every NOAA station in Utah · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00421240; 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 Castle Valley?
In a normal year in Castle Valley, 84 days a year reach 90°F (18 of them 100°F or more) and 118 nights fall to 32°F or colder.
- Days at 90°F or more
- 84a normal year
- Days at 100°F or more
- 18a normal year
- Nights at 32°F or colder
- 118a normal year
- Days that stay below freezing
- 15high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USC00421240.
How sunny is Castle Valley?
Over a year 85% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Castle Valley, 5.3 kWh per square metre a day. June is the sunniest month (91%) and December the cloudiest (76%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 78% | 2.7 |
| February | 77% | 3.6 |
| March | 83% | 5.2 |
| April | 84% | 6.5 |
| May | 86% | 7.5 |
| June | 91% | 8.3 |
| July | 88% | 7.5 |
| August | 87% | 6.7 |
| September | 89% | 5.8 |
| October | 87% | 4.3 |
| November | 84% | 3.1 |
| December | 76% | 2.3 |
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 much heating and cooling does Castle Valley need?
A normal year in Castle Valley brings 5,260 heating degree days, 2% fewer than the median U.S. place (5,373), and 1,520 cooling degree days, 67% more 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 4,021 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,136 | 0 |
| February | 822 | 0 |
| March | 598 | 0 |
| April | 358 | 4 |
| May | 125 | 71 |
| June | 14 | 310 |
| July | 1 | 510 |
| August | 0 | 420 |
| September | 48 | 188 |
| October | 330 | 16 |
| November | 720 | 0 |
| December | 1,109 | 0 |
| Year (annual) | 5,260 | 1,520 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00421240. 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 Castle Valley been warmer than normal lately?
2023 averaged 54.4°F, 0.3°F below the 1991-2020 normal of 54.7°F. 1 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 56.0°F | +1.3°F | 13.25 |
| 2022 | 54.5°F | −0.2°F | 13.55 |
| 2023 | 54.4°F | −0.3°F | 8.73 |
Source: observed years: ACIS, station USC00421240. A year counts only with all twelve months complete.
How does Castle Valley's climate compare?
Castle Valley is warmer than 87 of the other 96 places with their own NOAA record in Utah, and wetter than 40. Across the 7,247 U.S. stations with normals, its annual mean of 54.7°F is warmer than 59%.
In the Köppen classification computed from these normals, Castle Valley is BSk: cold semi-arid steppe. 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.
What do Castle Valley's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Castle Valley. This page uses Castle Valley (1 mi SE); the other differs by site and elevation:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Castle Valley station USC00421241 | 2 mi N | 4,725 ft | 55.5°F | 20°F | 96°F | 9.8 | 15 | April 17 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Castle Valley's climate
What is the coldest month in Castle Valley?
January, with a normal high of 39°F and a normal low of 18°F. The warmest is July (95°F by day, 68°F at night).
Does it snow in Castle Valley?
Yes. NOAA publishes no 1991-2020 snowfall normal for Castle Valley's NOAA station; Castle Valley's own co-op station Castle Valley station records 15 inches of snow in a normal year.
What is the rainiest month in Castle Valley?
October, with 1.48 in of precipitation in a normal year; the driest is June with 0.59 in.
What plant hardiness zone is Castle Valley in?
The USDA's 2023 map puts Castle Valley in zone 7a in ZIP code 84532, the nearest ZIP area.
How late can frost come in Castle Valley?
In half of years the last 32°F night comes after April 19; in one year in ten it comes after May 3. Waiting until May 3 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Utah climateThe statewide normals and every place in the state
- Moab, UT9 miles from this station, 57.6°F a year
- Arches National Park Headquarters, UT12 miles from this station, 58.0°F a year
- Dewey, UT14 miles from this station, 55.0°F a year
- Moab Canyonland Airport, UT22 miles from this station, 54.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made