Boulder, Wyoming climate: Normal weather by month, frost dates and records
Boulder's normal year runs from −7°F January nights to 82°F July afternoons, with 9.3 inches of precipitation and 42 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 2.2°C, January lows of −22°C, July highs of 28°C, 237 mm of precipitation a year.
- NOAA stationBoulder Rearing Station
- Station IDUSC00480951
- Location42.72°N 109.69°W
- Elevation6,940 ft (2,115 m)
- Population (census place)0
On October 14, the normal high in Boulder is 59°F and the normal low 20°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 Boulder.
- Jan 27° -7°
- Feb 31° -5°
- Mar 42° 9°
- Apr 53° 20°
- May 63° 28°
- Jun 73° 36°
- Jul 82° 41°
- Aug 81° 39°
- Sep 71° 30°
- Oct 58° 20°
- Nov 42° 8°
- Dec 29° -4°
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 Boulder each month?
July is the warmest month, with normal highs of 82°F; January the coldest, with normal lows of −7°F. The most precipitation falls in May (1.44 in), the least in November (0.45 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 27°F | −7°F | 9.9°F | 0.48 | 6.8 | 6 | <1 | 31 | 9 h 20 min |
| February | 31°F | −5°F | 13.1°F | 0.51 | 7.3 | 6 | <1 | 28 | 10 h 30 min |
| March | 42°F | 9°F | 25.5°F | 0.53 | 5.3 | 5 | <1 | 31 | 11 h 50 min |
| April | 53°F | 20°F | 36.5°F | 0.88 | 4.9 | 7 | <1 | 29 | 13 h 20 min |
| May | 63°F | 28°F | 45.6°F | 1.44 | 1.9 | 9 | <1 | 20 | 14 h 40 min |
| June | 73°F | 36°F | 54.3°F | 1.26 | 0.2 | 7 | <1 | 7 | 15 h 20 min |
| July | 82°F | 41°F | 61.1°F | 0.71 | 0.0 | 5 | 2 | 1 | 15 h |
| August | 81°F | 39°F | 59.5°F | 0.73 | 0.0 | 6 | 1 | 3 | 14 h |
| September | 71°F | 30°F | 50.8°F | 1.00 | 0.3 | 7 | <1 | 18 | 12 h 30 min |
| October | 58°F | 20°F | 38.8°F | 0.88 | 3.6 | 5 | <1 | 29 | 11 h 10 min |
| November | 42°F | 8°F | 24.7°F | 0.45 | 4.9 | 5 | <1 | 30 | 9 h 50 min |
| December | 29°F | −4°F | 12.5°F | 0.46 | 6.9 | 7 | <1 | 31 | 9 h |
| Year (annual) | 54°F | 18°F | 36.0°F | 9.33 | 42.1 | 75 | 2 | 258 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −3°C | −22°C | −12.3°C | 12 mm | 17 cm |
| February | −1°C | −20°C | −10.5°C | 13 mm | 19 cm |
| March | 5°C | −13°C | −3.6°C | 13 mm | 13 cm |
| April | 12°C | −7°C | 2.5°C | 22 mm | 12 cm |
| May | 17°C | −2°C | 7.6°C | 37 mm | 5 cm |
| June | 23°C | 2°C | 12.4°C | 32 mm | 1 cm |
| July | 28°C | 5°C | 16.2°C | 18 mm | 0 cm |
| August | 27°C | 4°C | 15.3°C | 19 mm | 0 cm |
| September | 22°C | −1°C | 10.4°C | 25 mm | 1 cm |
| October | 14°C | −7°C | 3.8°C | 22 mm | 9 cm |
| November | 5°C | −13°C | −4.1°C | 11 mm | 12 cm |
| December | −2°C | −20°C | −10.8°C | 12 mm | 18 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00480951; 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 Boulder?
Normal highs sit between 65°F and 85°F in June, July, August and September. Of those, July 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 USC00480951.
How hot and how cold does it get in Boulder?
In a normal year in Boulder, 2 days a year reach 90°F, 258 nights fall to 32°F or colder and 75 days bring measurable precipitation.
- Days at 90°F or more
- 2a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 258a normal year
- Days that stay below freezing
- 70high of 32°F or less
- Days with 0.01 inch of precipitation
- 75a normal year
- Days with 1 inch of snow or more
- 21a normal year
The highest temperature in this station's record (since 1989) is 97°F, on July 15, 2026; the lowest is −52°F, on December 22, 1990.
The wettest calendar year on that record is 1995, with 14.88 in; the snowiest season is 2016–17, with 67.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00480951; records: ACIS (NOAA Regional Climate Centers), station USC00480951. Records use complete months only; a month missing more than three days is left out.
How sunny is Boulder?
Over a year 79% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Boulder, 4.7 kWh per square metre a day. July is the sunniest month (85%) and April the cloudiest (72%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 78% | 2.3 |
| February | 76% | 3.2 |
| March | 73% | 4.3 |
| April | 72% | 5.4 |
| May | 74% | 6.4 |
| June | 83% | 7.5 |
| July | 85% | 7.4 |
| August | 85% | 6.5 |
| September | 83% | 5.2 |
| October | 78% | 3.5 |
| November | 75% | 2.4 |
| December | 72% | 1.9 |
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 Boulder need?
A normal year in Boulder brings 10,552 heating degree days, 96% more than the median U.S. place (5,373), and 25 cooling degree days, 97% fewer than the median (908). Ten months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 945 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,708 | 0 |
| February | 1,453 | 0 |
| March | 1,225 | 0 |
| April | 855 | 0 |
| May | 601 | 0 |
| June | 322 | 1 |
| July | 136 | 16 |
| August | 177 | 8 |
| September | 428 | 0 |
| October | 812 | 0 |
| November | 1,209 | 0 |
| December | 1,626 | 0 |
| Year (annual) | 10,552 | 25 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00480951. 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 Boulder been warmer than normal lately?
2025 averaged 39.4°F, 3.4°F above the 1991-2020 normal of 36.0°F. 3 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 38.3°F | +2.3°F | 9.72 | 38.5 |
| 2022 | 35.8°F | −0.2°F | 7.98 | 37.4 |
| 2023 | 34.6°F | −1.4°F | 10.36 | 58.5 |
| 2024 | 38.6°F | +2.6°F | 6.21 | 30.1 |
| 2025 | 39.4°F | +3.4°F | 9.23 | 40.5 |
Over 30 complete years from 1992 to 2025, the station's annual mean temperature rose at a fitted 3.3°F per century (+0.18°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00480951; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Boulder's climate compare?
Boulder is warmer than 2 of the other 70 places with their own NOAA record in Wyoming, and wetter than 16. Across the 7,247 U.S. stations with normals, its annual mean of 36.0°F is warmer than 2%.
In the Köppen classification computed from these normals, Boulder 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.
Questions about Boulder's climate
What is the coldest month in Boulder?
January, with a normal high of 27°F and a normal low of −7°F. The warmest is July (82°F by day, 41°F at night).
Does it snow in Boulder?
Yes: 42 inches in a normal year, falling on 29 days with 0.1 inch or more, the most in February (7.3 inches).
What is the rainiest month in Boulder?
May, with 1.44 in of precipitation in a normal year; the driest is November with 0.45 in.
What plant hardiness zone is Boulder in?
The USDA's 2023 map puts Boulder in zone 4b in ZIP code 82941, the nearest ZIP area. By the same method at Boulder's NOAA station, the coldest night of a typical year reaches −31°F (29 years, 1991-2020): zone 3b.
Nearby and next
- Wyoming climateThe statewide normals and every place in the state
- Pinedale, WY14 miles from this station, 37.5°F a year
- Cora, WY23 miles from this station, 35.1°F a year
- Big Piney, WY23 miles from this station, 36.5°F a year
- Daniel, WY27 miles from this station, 32.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made