Climate Comfort Score
54/100
Moderate
NOAA 1991–2020 normals 35°F annual avg 2 stations
Boulder, CO Climate
Temperature, precipitation, and comfort score from NOAA NCEI 1991–2020 normals →
- 35°F
- Avg annual temp
- 54/100
- Comfort score
- 33.9"
- Annual precip
- 73d
- Growing season
30-year climate normals from 2 weather stations (1991-2020).
The climate verdict for Boulder
Boulder, Colorado averages 35°F a year and scores 54/100 on the comfort index - moderate, milder than 27% of U.S. cities.
- 35°F
- yearly average temperature, NOAA normal
- 54/100
- comfort score, milder than 27% of U.S. cities
- 33.9"
- precipitation, annual total
- 73 days
- frost-free growing season
Based on NOAA U.S. Climate Normals (1991–2020) - 30-year averages describing the typical year, not a forecast.
Avg Temperature
35°F (2°C)
Avg High
46°F
Avg Low
25°F
Annual Precip
33.9"
Comfort Score
54/100
Moderate
Avg Annual Temperature
35°F
30-year mean (NOAA NCEI)
Annual Precipitation
33.9"
Liquid-equivalent total
Comfort score vs national 100-point ceiling (Boulder) 54.0%
National median (63)
PlainClimate composite, temperature mildness, humidity, precipitation, extreme-weather frequency. Moderate for the Boulder area.
How Boulder compares to every U.S. city
Boulder's comfort score vs. all U.S. cities
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
54 Top 73% higher than 27% of 6,915 US cities
Each bar is a band; taller bars hold more US cities. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Warming context for Boulder
MethodologyZooming out from Boulder's own normal, the chart below shows how the U.S. land temperature anomaly has tracked the global mean since 1900 - the most recent decade sits warmer than the 30-year mean shown here.
- United States land mean (NOAA NCEI) +0.11 °C/decade
- Global anomaly (NASA GISTEMP) +0.11 °C/decade
- Paris Agreement thresholds 1.5°C / 2.0°C
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 |
Monthly Precipitation
Average monthly rainfall and snowfall
January 2.7"
14.1 days with precipitation
February 2.8"
17.8 days with precipitation
March 3.7"
15.8 days with precipitation
April 4.8"
17.5 days with precipitation
May 3.8"
15.8 days with precipitation
June 1.9"
11.4 days with precipitation
July 3.0"
14.4 days with precipitation
August 2.5"
13.8 days with precipitation
September 2.0"
9.2 days with precipitation
October 2.2"
10.5 days with precipitation
November 2.3"
11.1 days with precipitation
December 2.1"
15.5 days with precipitation
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
What Boulder's climate means for you
Boulder runs 35°F a year - peaking in July, coldest in February.
- Gardeners get about 73 frost-free days, with the last spring freeze near June 21 - plan the planting calendar around it, not the regional average.
- Energy bills track 10,824 heating and 0 cooling degree days a year, higher means the furnace or AC runs more.
- Comparing places to live? Line this city up against nearby cities and the national rankings. See rankings
These are 30-year NOAA normals (1991–2020) - the typical year, not a forecast for any specific season.
Climate Guides
Climate Insight: Boulder, CO
In Boulder, Colorado, the NOAA 1991–2020 climate normals put the annual average temperature at 35°F, ranging from a mean daily high of 46°F to a mean daily low of 25°F. July is typically the warmest month of the year, while February is the coldest. As thirty-year averages computed from 2 weather stations, these numbers smooth out year-to-year noise into a working baseline for a typical month.
Anyone planning to live, garden, or travel in Boulder should weigh precipitation alongside temperature: the annual average runs 33.9 inches, with seasonal snowfall possible. The frost-free season averages 73 days, which directly shapes the planting calendar and growing potential for the area, with the last spring freeze near June 21 and the first fall freeze near September 2. And on the energy front, 10,824 heating degree days and 0 cooling degree days tell the story of how often furnaces and air conditioners run during a normal year.
On PlainClimate's composite comfort index, Boulder scores 54/100 (Moderate), a blended measure that weighs temperature mildness, precipitation moderation, and extreme-weather frequency against one another. Shoulder seasons bring the mildest highs and lows in the monthly tables above, summer brings July-driven heat, and winter brings February-driven cold - use that rhythm for planning. These figures are thirty-year averages rather than forecasts, so a specific year may still run warmer, cooler, wetter, or drier than what's shown.
Frequently Asked Questions
What is the average temperature in Boulder, CO? ▼
The average annual temperature in Boulder, Colorado is 35°F. The warmest month averages 68°F (20°C) and the coldest averages 12°F (-11°C).
How much rain does Boulder get? ▼
Boulder receives 33.9 inches of precipitation annually. Based on NOAA 30-year climate normals (1991-2020).
What is the comfort score for Boulder? ▼
Boulder has a climate comfort score of 54/100 (Moderate), milder than 27% of U.S. cities in the PlainClimate database.
When is the growing season in Boulder? ▼
Boulder has approximately 73 frost-free days per year, with the last spring freeze around June 21 and the first fall freeze around September 2.
How much energy does heating and cooling require in Boulder? ▼
Boulder has 10,824 heating degree days and 0 cooling degree days annually, a heating-dominated climate. See our <a href="/guides/reading-weather-data/" class="underline hover:text-brand-600">guide to reading weather data</a> for what these figures mean.
Where does this Boulder climate data come from? ▼
NOAA U.S. Climate Normals v1.0.1 (1991-2020), from 2 weather stations near Boulder.
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). Station: USW00094075. For informational purposes only.
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainClimate Editorial
Every figure on PlainClimate is rendered directly from NOAA 1991-2020 U.S. Climate Normals data, no number is typed in by an editor. This page draws directly on NOAA 1991-2020 U.S. Climate Normals data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.