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Climate in Boulder, Colorado: Monthly Weather Averages

By the AverageClimate Editorial Team · Last updated: October 2026

Boulder sits at 5,484 feet above sea level, and its climate, as recorded at the Boulder, CO station, runs to a yearly mean of 51.5°F. The warmest month is July, averaging 72.5°F with typical highs of 88.0°F; the coldest is December, averaging 33.7°F with lows around 21.1°F. Across a normal year the city receives 21.2 in of precipitation and 92.8 in of snow. The full month-by-month picture below comes from the official 1991–2020 U.S. Climate Normals — the 30-year averages the National Weather Service itself uses — so it describes the Boulder climate you should actually plan around, whether you are timing a visit, weighing a move, or just settling an argument about which month is best.

Boulder climate month by month

The table below is the complete 1991–2020 normals profile for Boulder: average high, average low and mean temperature, rainfall, and snowfall for every month. Read down the Mean column to feel the year's rhythm — Boulder's temperature range runs from 33.7°F in December to 72.5°F in July.

How to read the colors:below freezingcoldcoolmildwarmhot. Bands are colored by each cell's own temperature, so a whole year reads at a glance.

Boulder through the seasons

Winter in Boulder averages highs of 46.3–48.3°F and lows of 21.1–22.3°F, a seasonal mean of 34.4°F. The three months together bring 2.6 in of precipitation — about 12% of the city's yearly total — with February the wettest of the three at 0.99 in. Snowfall averages 39.3 in over the season, most of it in February (15.0 in). It is a genuinely cold season — heavy coats, freezing nights, and the year's most changeable weather — without being locked below freezing around the clock.

Spring in Boulder averages highs of 57.0–71.3°F and lows of 29.0–42.7°F, a seasonal mean of 49.6°F. The three months together bring 8.2 in of precipitation — about 39% of the city's yearly total — with May the wettest of the three at 3.21 in. Snowfall averages 32.4 in over the season, most of it in March (15.7 in). The season is a transition: the average temperature climbs 14.0°F from March to May, and by late spring Boulder is firmly into mild territory, with May rainfall of 3.21 in to plan around.

Summer in Boulder averages highs of 82.5–88.0°F and lows of 51.1–57.0°F, a seasonal mean of 70.0°F. The three months together bring 5.5 in of precipitation — about 26% of the city's yearly total — with June the wettest of the three at 1.95 in. It is a warm, usable summer: afternoons are hot enough for swimming and lake or coast time, while evenings usually cool off comfortably.

Fall in Boulder averages highs of 54.5–78.8°F and lows of 28.1–48.1°F, a seasonal mean of 52.1°F. The three months together bring 4.9 in of precipitation — about 23% of the city's yearly total — with September the wettest of the three at 2.09 in. Snowfall averages 21.1 in over the season, most of it in November (13.1 in). Temperatures ease off through the season — the monthly mean drops 22.2°F from September to November — and fall is when Boulder's weather turns crisp and dry, with the first freezes arriving by November.

Best and worst months to visit Boulder

Ranking every month by its normals — mild mean temperatures score best, heavy rain and snow count against — the most comfortable months to visit Boulder are:

JuneJulyAugust

June leads the list: average highs of 82.5°F, lows of 51.1°F, and 1.95 in of rain, with snow a non-factor at 0.0 in. The other picks, July and August, offer the same balance in Boulder's mild stretch of the year. At the other end, December is usually the month to avoid — deep-winter cold, with a mean temperature of 33.7°F and 0.81 in of precipitation plus 13.0 in of snow.

How Boulder compares

Across the 114 cities in our dataset, the typical city averages 57.8°F for the year and 35.7 in of precipitation. Boulder runs 6.3°F cooler than that typical city and drier by 14.4 in a year, ranking #82 of 114 for annual warmth and #82 of 114 for precipitation (wettest first). Its year-round temperature swing — warmest month minus coldest — is 38.8°F, which puts it in the moderate, clearly seasonal camp.

Within Colorado, Boulder is the warmest of the cities we track. See the Colorado climate overview for the full state comparison, including Boulder (warmest, 51.5°F yearly mean) and Colorado Springs (coolest, 50.4°F).

Planning notes for Boulder

For anyone relocating: average overnight lows drop below freezing in 5 months (January, February, March, November, December), so heating, winter tires, and pipe protection are real seasonal concerns; highs reach the 80s on average in 3 months, but 90°F average highs never arrive; days and nights differ by 28.4°F on average — a big desert-style swing that rewards dressing in layers year-round; 5 months of the year average between 55°F and 80°F, the band most people find comfortable without heating or cooling. Those four facts, all straight from the normals table above, shape everything from a Boulder wardrobe to its utility bills.

Boulder climate FAQ

Source: 1991–2020 U.S. Climate Normals, NOAA National Centers for Environmental Information (NCEI) — ncei.noaa.gov. Station: Boulder, CO (USC00050848), elevation 5,484 ft. Figures checked October 2026.