Boysen Dam, Wyoming climate: Climate normals at a NOAA weather station
Boysen Dam's normal year runs from 5°F January nights to 91°F July afternoons, with 9.0 inches of precipitation and 16 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.0°C, January lows of −15°C, July highs of 33°C, 229 mm of precipitation a year.
- NOAA stationBoysen Dam
- Station IDUSC00481000
- Location43.41°N 108.16°W
- Elevation4,875 ft (1,486 m)
On October 23, the normal high in Boysen Dam is 57°F and the normal low 32°F, and the chance of measurable rain or snow is 12%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Boysen Dam.
- Jan 30° 5°
- Feb 37° 11°
- Mar 50° 23°
- Apr 59° 33°
- May 69° 43°
- Jun 81° 52°
- Jul 91° 60°
- Aug 89° 57°
- Sep 77° 47°
- Oct 60° 35°
- Nov 44° 22°
- Dec 31° 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 at Boysen Dam each month?
July is the warmest month, with normal highs of 91°F; January the coldest, with normal lows of 5°F. The most precipitation falls in May (2.08 in), the least in January (0.22 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 30°F | 5°F | 17.5°F | 0.22 | 2.8 | 3 | <1 | 31 | 9 h 20 min |
| February | 37°F | 11°F | 24.0°F | 0.32 | 3.2 | 4 | <1 | 28 | 10 h 30 min |
| March | 50°F | 23°F | 36.8°F | 0.57 | 3.8 | 4 | <1 | 27 | 11 h 50 min |
| April | 59°F | 33°F | 45.7°F | 1.10 | 1.3 | 6 | <1 | 14 | 13 h 20 min |
| May | 69°F | 43°F | 55.7°F | 2.08 | 0.1 | 8 | 1 | 3 | 14 h 40 min |
| June | 81°F | 52°F | 66.3°F | 1.01 | 0.0 | 6 | 6 | <1 | 15 h 20 min |
| July | 91°F | 60°F | 75.1°F | 0.75 | 0.0 | 5 | 20 | <1 | 15 h 10 min |
| August | 89°F | 57°F | 73.0°F | 0.46 | 0.0 | 4 | 17 | <1 | 14 h |
| September | 77°F | 47°F | 61.8°F | 0.96 | 0.1 | 5 | 3 | 1 | 12 h 30 min |
| October | 60°F | 35°F | 47.5°F | 0.90 | 0.8 | 4 | <1 | 11 | 11 h 10 min |
| November | 44°F | 22°F | 33.2°F | 0.28 | 1.8 | 3 | <1 | 28 | 9 h 40 min |
| December | 31°F | 9°F | 20.1°F | 0.37 | 2.2 | 4 | <1 | 31 | 9 h |
| Year (annual) | 60°F | 33°F | 46.4°F | 9.02 | 16.1 | 56 | 47 | 172 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −1°C | −15°C | −8.1°C | 6 mm | 7 cm |
| February | 3°C | −12°C | −4.4°C | 8 mm | 8 cm |
| March | 10°C | −5°C | 2.7°C | 14 mm | 10 cm |
| April | 15°C | 0°C | 7.6°C | 28 mm | 3 cm |
| May | 20°C | 6°C | 13.2°C | 53 mm | 0 cm |
| June | 27°C | 11°C | 19.1°C | 26 mm | 0 cm |
| July | 33°C | 15°C | 23.9°C | 19 mm | 0 cm |
| August | 31°C | 14°C | 22.8°C | 12 mm | 0 cm |
| September | 25°C | 8°C | 16.6°C | 24 mm | 0 cm |
| October | 16°C | 1°C | 8.6°C | 23 mm | 2 cm |
| November | 7°C | −5°C | 0.7°C | 7 mm | 5 cm |
| December | 0°C | −13°C | −6.6°C | 9 mm | 6 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00481000; 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 Boysen Dam?
Normal highs sit between 65°F and 85°F in May, June and September. Of those, September has the fewest days with rain (5).
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 USC00481000.
When is the last frost at Boysen Dam?
In Boysen Dam, the last spring frost (32°F) comes after May 5 in half of years and after May 20 in one year in ten; the first autumn frost comes before October 7 in half of years and before September 24 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 51 year in 10 after May 20; 9 in 10 after April 23
- First autumn frost, half of years before
- October 71 year in 10 before September 24; 9 in 10 before October 20
NOAA puts the median frost-free season at 153 days, and the season without a hard freeze (28°F) at 174 days.
A hard freeze (28°F) comes after April 26 in half of springs and before October 17 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Boysen Dam in zone 4b in ZIP code 82649, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, the station is in zone 5a: the coldest night of a typical year reaches −18°F (21 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in Wyoming · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00481000; 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 at Boysen Dam?
In a normal year in Boysen Dam, 47 days a year reach 90°F (3 of them 100°F or more), 172 nights fall to 32°F or colder and 56 days bring measurable precipitation.
- Days at 90°F or more
- 47a normal year
- Days at 100°F or more
- 3a normal year
- Nights at 32°F or colder
- 172a normal year
- Days that stay below freezing
- 51high of 32°F or less
- Days with 0.01 inch of precipitation
- 56a normal year
- Days with 1 inch of snow or more
- 7a normal year
The highest temperature in this station's record (since 1948) is 107°F, on July 13, 2026; the lowest is −39°F, on January 31, 1979.
The wettest calendar year on that record is 2016, with 14.06 in; the snowiest season is 1997–98, with 31.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00481000; records: ACIS (NOAA Regional Climate Centers), station USC00481000. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Boysen Dam?
Over a year 80% of the sunlight that would reach the ground under clear skies gets through the clouds at Boysen Dam, 4.6 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (71%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 77% | 2.1 |
| February | 77% | 3.1 |
| March | 76% | 4.3 |
| April | 75% | 5.5 |
| May | 76% | 6.4 |
| June | 84% | 7.5 |
| July | 87% | 7.3 |
| August | 86% | 6.4 |
| September | 85% | 5.1 |
| October | 78% | 3.4 |
| November | 76% | 2.3 |
| December | 71% | 1.7 |
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 Boysen Dam record?
A normal year at Boysen Dam brings 7,515 heating degree days, 40% more than the median U.S. place (5,373), and 769 cooling degree days, 15% 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 2,710 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,471 | 0 |
| February | 1,149 | 0 |
| March | 873 | 0 |
| April | 580 | 1 |
| May | 305 | 17 |
| June | 74 | 113 |
| July | 6 | 319 |
| August | 15 | 261 |
| September | 154 | 58 |
| October | 545 | 1 |
| November | 953 | 0 |
| December | 1,392 | 0 |
| Year (annual) | 7,515 | 769 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00481000. 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.
Have recent years at Boysen Dam been warmer than normal?
2025 averaged 49.1°F, 2.7°F above the 1991-2020 normal of 46.4°F. 3 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 48.7°F | +2.3°F | 7.65 | 26.1 |
| 2022 | 46.1°F | −0.3°F | 9.66 | 30.4 |
| 2023 | 43.6°F | −2.8°F | 14.02 | 24.3 |
| 2024 | 48.9°F | +2.5°F | 5.73 | 6.5 |
| 2025 | 49.1°F | +2.7°F | 10.74 | 7.2 |
Over 47 complete years from 1950 to 2025, the station's annual mean temperature rose at a fitted 1.8°F per century (+0.10°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00481000; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Boysen Dam's climate compare?
Boysen Dam is warmer than 55 of the 71 places with their own NOAA record in Wyoming, and wetter than 15. Across the 7,247 U.S. stations with normals, its annual mean of 46.4°F is warmer than 25%.
In the Köppen classification computed from these normals, Boysen Dam 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.
Questions about Boysen Dam's climate
What is the coldest month at Boysen Dam?
January, with a normal high of 30°F and a normal low of 5°F. The warmest is July (91°F by day, 60°F at night).
Does it snow at Boysen Dam?
Yes: 16 inches in a normal year, falling on 11 days with 0.1 inch or more, the most in March (3.8 inches).
What is the rainiest month at Boysen Dam?
May, with 2.08 in of precipitation in a normal year; the driest is January with 0.22 in.
What plant hardiness zone is Boysen Dam in?
The USDA's 2023 map puts Boysen Dam in zone 4b in ZIP code 82649, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches −18°F (21 years, 1991-2020): zone 5a.
How late can frost come at Boysen Dam?
In half of years the last 32°F night comes after May 5; 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
- Wyoming climateThe statewide normals and every place in the state
- Shoshoni, WY12 miles from this station, 45.6°F a year
- Thermopolis, WY17 miles from this station, 48.6°F a year
- Black Mountain, WY27 miles from this station, 46.8°F a year
- Riverton, WY28 miles from this station, 44.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made