Boulder, Utah climate: Normal weather by month, frost dates and records
Boulder's normal year runs from 21°F December nights to 84°F July afternoons, with 11.8 inches of precipitation and 52 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.2°C, December lows of −6°C, July highs of 29°C, 301 mm of precipitation a year.
- NOAA stationBoulder
- Station IDUSC00420849
- Location37.91°N 111.42°W
- Elevation6,650 ft (2,027 m)
- From the center1 miles
- Population244
On October 22, the normal high in Boulder is 60°F and the normal low 38°F, and the chance of measurable rain or snow is 15%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Boulder.
- Jan 40° 21°
- Feb 44° 25°
- Mar 53° 31°
- Apr 60° 36°
- May 68° 45°
- Jun 79° 54°
- Jul 84° 61°
- Aug 81° 60°
- Sep 74° 52°
- Oct 62° 41°
- Nov 49° 30°
- Dec 39° 21°
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 84°F; December the coldest, with normal lows of 21°F. The most precipitation falls in August (1.73 in), the least in June (0.38 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 40°F | 21°F | 30.4°F | 1.07 | 15.7 | 6 | <1 | 30 | 9 h 50 min |
| February | 44°F | 25°F | 34.1°F | 1.05 | 10.8 | 6 | <1 | 25 | 10 h 50 min |
| March | 53°F | 31°F | 41.7°F | 0.91 | 6.7 | 5 | <1 | 20 | 11 h 50 min |
| April | 60°F | 36°F | 47.7°F | 0.51 | 2.3 | 4 | <1 | 12 | 13 h 10 min |
| May | 68°F | 45°F | 56.4°F | 0.72 | 0.4 | 5 | <1 | 3 | 14 h 10 min |
| June | 79°F | 54°F | 66.6°F | 0.38 | 0.0 | 3 | 1 | <1 | 14 h 50 min |
| July | 84°F | 61°F | 72.4°F | 1.11 | 0.0 | 8 | 5 | <1 | 14 h 30 min |
| August | 81°F | 60°F | 70.4°F | 1.73 | 0.0 | 10 | 2 | <1 | 13 h 40 min |
| September | 74°F | 52°F | 63.0°F | 1.58 | 0.0 | 7 | <1 | <1 | 12 h 30 min |
| October | 62°F | 41°F | 51.5°F | 1.44 | 0.5 | 5 | <1 | 6 | 11 h 20 min |
| November | 49°F | 30°F | 39.5°F | 0.56 | 3.5 | 3 | <1 | 20 | 10 h 10 min |
| December | 39°F | 21°F | 30.2°F | 0.79 | 11.7 | 5 | <1 | 30 | 9 h 30 min |
| Year (annual) | 61°F | 40°F | 50.3°F | 11.85 | 51.6 | 67 | 8 | 146 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 4°C | −6°C | −0.9°C | 27 mm | 40 cm |
| February | 6°C | −4°C | 1.2°C | 27 mm | 27 cm |
| March | 12°C | −1°C | 5.4°C | 23 mm | 17 cm |
| April | 15°C | 2°C | 8.7°C | 13 mm | 6 cm |
| May | 20°C | 7°C | 13.6°C | 18 mm | 1 cm |
| June | 26°C | 12°C | 19.2°C | 10 mm | 0 cm |
| July | 29°C | 16°C | 22.4°C | 28 mm | 0 cm |
| August | 27°C | 15°C | 21.3°C | 44 mm | 0 cm |
| September | 23°C | 11°C | 17.2°C | 40 mm | 0 cm |
| October | 17°C | 5°C | 10.8°C | 37 mm | 1 cm |
| November | 10°C | −1°C | 4.2°C | 14 mm | 9 cm |
| December | 4°C | −6°C | −1.0°C | 20 mm | 30 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00420849; 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 May, June, July, August and September. Of those, June has the fewest days with rain (3).
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 USC00420849.
When is the last frost in Boulder?
In Boulder, the last spring frost (32°F) comes after May 4 in half of years and after May 25 in one year in ten; the first autumn frost comes before October 14 in half of years and before September 30 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 41 year in 10 after May 25; 9 in 10 after April 20
- First autumn frost, half of years before
- October 141 year in 10 before September 30; 9 in 10 before October 29
NOAA puts the median frost-free season at 160 days, and the season without a hard freeze (28°F) at 182 days.
A hard freeze (28°F) comes after April 23 in half of springs and before October 23 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Boulder in zone 7a in ZIP code 84716, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Boulder's NOAA station is in zone 7a: the coldest night of a typical year reaches 3°F (30 complete years).
Frost dates for every NOAA station in Utah · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00420849; 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 in Boulder?
In a normal year in Boulder, 8 days a year reach 90°F, 146 nights fall to 32°F or colder and 67 days bring measurable precipitation.
- Days at 90°F or more
- 8a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 146a normal year
- Days that stay below freezing
- 14high of 32°F or less
- Days with 0.01 inch of precipitation
- 67a normal year
- Days with 1 inch of snow or more
- 15a normal year
The highest temperature in this station's record (since 1954) is 97°F, on June 16, 2021; the lowest is −17°F, on February 6, 1989.
The wettest calendar year on that record is 1957, with 20.01 in; the snowiest season is 2009–10, with 157.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00420849; records: ACIS (NOAA Regional Climate Centers), station USC00420849. Records use complete months only; a month missing more than three days is left out.
How sunny is Boulder?
Over a year 85% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Boulder, 5.3 kWh per square metre a day. June is the sunniest month (91%) and February the cloudiest (78%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 80% | 2.8 |
| February | 78% | 3.7 |
| March | 84% | 5.3 |
| April | 85% | 6.6 |
| May | 86% | 7.5 |
| June | 91% | 8.3 |
| July | 85% | 7.3 |
| August | 84% | 6.5 |
| September | 88% | 5.8 |
| October | 86% | 4.4 |
| November | 85% | 3.2 |
| December | 78% | 2.5 |
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 5,906 heating degree days, 10% more than the median U.S. place (5,373), and 580 cooling degree days, 36% 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 2,651 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,073 | 0 |
| February | 867 | 0 |
| March | 721 | 0 |
| April | 518 | 0 |
| May | 282 | 14 |
| June | 60 | 108 |
| July | 5 | 234 |
| August | 9 | 177 |
| September | 106 | 46 |
| October | 422 | 2 |
| November | 767 | 0 |
| December | 1,079 | 0 |
| Year (annual) | 5,906 | 580 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00420849. 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 52.9°F, 2.6°F above the 1991-2020 normal of 50.3°F. 2 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 51.6°F | +1.3°F | 11.23 | 43.0 |
| 2023 | 49.4°F | −0.9°F | 14.07 | 87.8 |
| 2025 | 52.9°F | +2.6°F | 10.02 | 15.7 |
Over 61 complete years from 1955 to 2025, the station's annual mean temperature rose at a fitted 4.2°F per century (+0.24°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00420849; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Boulder's climate compare?
Boulder is warmer than 53 of the other 96 places with their own NOAA record in Utah, and wetter than 39. Across the 7,247 U.S. stations with normals, its annual mean of 50.3°F is warmer than 42%.
In the Köppen classification computed from these normals, Boulder 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 Boulder's climate
What is the coldest month in Boulder?
December, with a normal high of 39°F and a normal low of 21°F. The warmest is July (84°F by day, 61°F at night).
Does it snow in Boulder?
Yes: 52 inches in a normal year, falling on 16 days with 0.1 inch or more, the most in January (15.7 inches).
What is the rainiest month in Boulder?
August, with 1.73 in of precipitation in a normal year; the driest is June with 0.38 in.
What plant hardiness zone is Boulder in?
The USDA's 2023 map puts Boulder in zone 7a in ZIP code 84716, the nearest ZIP area. By the same method at Boulder's NOAA station, the coldest night of a typical year reaches 3°F (30 years, 1991-2020): zone 7a.
How late can frost come in Boulder?
In half of years the last 32°F night comes after May 4; in one year in ten it comes after May 25. Waiting until May 25 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Utah climateThe statewide normals and every place in the state
- Escalante, UT14 miles from this station, 51.9°F a year
- Capitol Reef National Park, UT28 miles from this station, 53.7°F a year
- Torrey, UT29 miles from this station, 51.1°F a year
- Loa, UT37 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