Boulder, CO Climate: Temperature & Rain by Month
Temperature and precipitation from NOAA NCEI 1991–2020 normals →, plus PlainClimate's derived comfort score
30-year climate normals (1991-2020) from Boulder's primary NOAA station, BOULDER 14 W - 2 stations mapped to the area.
The climate verdict for Boulder
Boulder, Colorado has a mixed annual climate rather than one dominant extreme. Its NOAA normal shows an annual average of 35°F. At 52/100 (moderate) the climate comfort score falls in the bottom third of the station-mapped U.S. score corpus, exceeding only 24% of scores.
- 35°F
- yearly average temperature, NOAA normal
- 52/100
- comfort score, above 24% of station-mapped location scores
- 33.9"
- precipitation, annual total
- 73 days
- frost-free growing season
Boulder: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USW00094075 · Boulder, CO 35°F mean · 33.9" precip
TEMP-COLD · RANK-COOL · PHOTO-FINISH · PRCP-MID · SWING-MID · COMF-LOW · LOAD-HEAT · STN-MULTI · BOOK-FULL
- TEMP-COLD 35°F
- RANK-COOL #69
- PHOTO-FINISH ≈ Cora
- PRCP-MID 33.9"
- SWING-MID 36°F
- COMF-LOW 52/100
- LOAD-HEAT 10,824 HDD
- STN-MULTI USW00094075
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Cora, WY ( -0.1 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every CO station list.
- Boulder (this station) 35°F
- Cold Cora, WY 35°F
- Hot Eagle Rvr Natur…, AK 35°F
- Near St. Paul, AK 35°F
- Near Lazy Mtn, AK 35°F
Climate Living Index · Boulder
Boulder: 19/100 · grade F
Boulder publishes 4 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 2 missing weights rescale to 100.
PlainClimate-derived for Boulder, not an official NOAA rating. Rankings still use Comfort Score 52/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Precipitation balance | 33.9 in · 1.1 from 35 in | 94/100 · A |
| Annual temperature balance | 35.2°F · 32.3° from 67.5°F | 0/100 · F |
| Frost-free season | 73 days/year | 0/100 · F |
| Normal heat + freeze calendar | 251 calendar days | 0/100 · F |
Boulder · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Boulder is a continental Köppen climate: Dfc
Coldest-month mean 19.6°F and warmest-month mean 55.2°F place this station in continental, no dry season, cool summer climates (Dfc). Class Dfc is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: continental, specifically continental, no dry season, cool summer.
- Köppen code
- Dfc
- Group
- Continental
- Warmest month
- 55.2°F
- Coldest month
- 19.6°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Boulder sits across the climate record
Three NOAA fields for Boulder's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- Cooler than 99%
- Among 6,861 stations, Boulder sits in the cooler third of annual means.
- Annual precipitation
- 46th percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Narrower than 81%
- Warmest-to-coldest month gap for Boulder is compact versus 6,861 complete station-years.
How Boulder compares across U.S. station-mapped locations
Boulder's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
52 24th percentile score exceeds 24% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). This entry sits in this band.
- 60–70: 1,236 station-mapped locations (20%). Above this entry.
- 70–80: 650 station-mapped locations (11%). Above this entry.
- 80–90: 921 station-mapped locations (15%). Above this entry.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Snow | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|---|
| January | 29°F (-2°C) | 12°F (-11°C) | 20°F (-7°C) | 2.7" | N/A | 30.9 | 0.0 |
| February | 28°F (-2°C) | 12°F (-11°C) | 20°F (-7°C) | 2.8" | N/A | 27.7 | 0.0 |
| March | 36°F (2°C) | 17°F (-8°C) | 26°F (-3°C) | 3.7" | N/A | 30.0 | 0.0 |
| April | 40°F (5°C) | 22°F (-6°C) | 31°F (-1°C) | 4.8" | N/A | 28.3 | 0.0 |
| May | 50°F (10°C) | 29°F (-2°C) | 39°F (4°C) | 3.8" | N/A | 25.0 | 0.0 |
| June | 62°F (17°C) | 36°F (2°C) | 49°F (9°C) | 1.9" | N/A | 6.3 | 0.0 |
| July | 68°F (20°C) | 43°F (6°C) | 55°F (13°C) | 3.0" | N/A | 0.3 | 0.0 |
| August | 66°F (19°C) | 41°F (5°C) | 53°F (12°C) | 2.5" | N/A | 1.4 | 0.0 |
| September | 59°F (15°C) | 34°F (1°C) | 46°F (8°C) | 2.0" | N/A | 10.9 | 0.0 |
| October | 47°F (8°C) | 26°F (-3°C) | 36°F (2°C) | 2.2" | N/A | 24.8 | 0.0 |
| November | 35°F (2°C) | 19°F (-7°C) | 27°F (-3°C) | 2.3" | N/A | 27.7 | 0.0 |
| December | 28°F (-2°C) | 12°F (-11°C) | 20°F (-7°C) | 2.1" | N/A | 30.9 | 0.0 |
The year, day by day
Summer here tops out rather than builds: the warmest normal high is 69°F around July 19, short of 90°F on every date, while 251 dates carry a normal low at or below freezing, the coldest 11°F near December 19.
The freezing stretch
The normal low stays at or below 32°F into May 29, then returns to freezing around September 22, covering 251 dates in all.
Derived from the normal daily minimum. This is a different measure from the 50%-probability frost dates shown elsewhere on this page, which come from NOAA’s frost product.
Where the wet dates fall
The likeliest wet date is February 16, when 58% of years recorded at least a hundredth of an inch. The driest is September 26 at 31%. Summed across the calendar, that is about 167 wet dates a year.
The widest day
June 23 carries the biggest normal gap between afternoon and dawn, 27°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Boulder.
Where Boulder Stands Nationally
Winters bite deep and often: the normal nightly low dips to freezing or below on around 251 nights a year, placing this among the most frost-prone tenth of ranked stations.
Boulder earns one nationally notable standing (outer quintile) against 6,860 NOAA 1991–2020 normals stations, middle-of-the-pack metrics stay silent here.
Monthly Precipitation
Average monthly rainfall and snowfall
14.1 days with precipitation
17.8 days with precipitation
15.8 days with precipitation
17.5 days with precipitation
15.8 days with precipitation
11.4 days with precipitation
14.4 days with precipitation
13.8 days with precipitation
9.2 days with precipitation
10.5 days with precipitation
11.1 days with precipitation
15.5 days with precipitation
Boulder spreads its precipitation across the year
Neither half of the year dominates here: June through August take 22% of the annual total and December through February 22%, with neither reaching the 35% that would mark a distinct wet season. Boulder has no dry season to plan around, though it does carry a 35.6°F seasonal spread.
The gap between the wettest and driest month still matters: April averages 4.8" and June 1.9". The three wettest months together take 36% of the year, against the 25% a perfectly flat distribution would give them.
Shares are computed from this station's own 1991-2020 monthly precipitation normals. "Spread across the year" means neither the June-August nor the December-February share reaches 35%; it describes an average year, not the variability of any single one.
How Boulder's precipitation splits across the calendar
About 167 days a year record measurable precipitation here, carrying 33.9" between them, or roughly 0.20 inches on a typical wet day. That sits in the middle band: neither the many-light-days pattern of the Pacific Northwest and the Great Lakes, nor the few-heavy-events pattern of the Gulf and the desert Southwest.
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year and say nothing about the heaviest single storm on record.
Frost Dates & Growing Season
First Fall Freeze
September 2
50% probability date
Last Spring Freeze
June 21
50% probability date
Growing Season
73 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
10,824
Higher = more heating needed
Cooling Degree Days
0
Higher = more cooling needed
Warmest Month
July
Coldest Month
February
Nationwide similar cities
Other rankable U.S. places outside CO closest to Boulder on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (35°F here).
- Wisdom, MT 35°F · 0.0°F off
- Cora, WY 35°F · 0.1°F off
- St. Paul, AK 35°F · 0.2°F off
- Orr, MN 36°F · 0.4°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (33.9" here), excluding temperature-peer places.
- Chilton, WI 33.9" · 0.0" off
- Jefferson, OK 33.9" · 0.0" off
- Mankato, MN 33.9" · 0.0" off
- Port Washington, WI 33.9" · 0.0" off
Data-derived climate profile
How Boulder's climate pattern fits together
heating led · moderate · mid swing
Boulder's energy balance leans toward cold weather: 10,824 annual heating degree days against 0 for cooling. Its 35.6°F seasonal range still makes the monthly rows more useful than the annual average alone.
Only about 73 days are frost-free in a normal year. That short interval is consistent with the cold-season signal, but the measure does not predict the exact first or last freeze in any one year.
July and February mark the typical warm and cold ends of the calendar in Boulder's middle-range seasonal profile. The measured spread is 35.6°F. The annual average is 35°F. Neither the annual mean nor one extreme month represents the full calendar on its own.
Boulder's 33.9 inches of annual precipitation falls in PlainClimate's middle band, so “wet” or “dry” is not the leading description. Snowfall is not added to the interpretation because its annual value is missing. Temperature balance and the calendar distribution carry more information than the annual moisture label alone.
These labels group NOAA 1991-2020 normals from Boulder's primary station, so the winter figures are a thirty-year average and not a floor: a single hard season can run well below them. Treat each band as a descriptive range for Boulder, not an official NOAA class or a year-ahead forecast.
Questions about Boulder's climate
How much rain does Boulder get? ▼
How cold does Boulder get in winter? ▼
How much energy does heating and cooling require in Boulder? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Boulder's primary station: BOULDER 14 W (USW00094075). 2 NOAA stations are mapped to the Boulder area; the primary station's record is used for consistency. For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The 2024 Census Gazetteer identifies the exact name-and-state match as an incorporated place (GEOID 0807850). Match rule for Boulder: exact normalized name + state only, no fuzzy expansion, so nearby differently spelled facilities stay unmatched.
On this page every temperature, precipitation, and derived score for Boulder comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.