Boulder in Fall
In fall (September, October and November), Boulder sees average daytime highs around 58°F and overnight lows near 33°F, with 5.3 in of precipitation over about 24 wet days across the season. It is the 2nd-warmest season and the 3rd-wettest season.
Over the season highs ease from about 75°F in early September to 41°F by late November. The sky is clear or mostly clear about 51% of the time across fall, and the air most often feels dry.
Fall is Boulder's 2nd-best season to visit on our travel score. For the whole year in context, see Boulder's year-round climate.
- Avg daytime high
- 58°F
- 2nd-warmest season
- Avg overnight low
- 33°F
- Precipitation
- 5.3 in
- 24 wet days
- Avg wind
- 5 mph
- Travel score
- 4.4
- 2nd-best season
- Months
- Sep · Oct · Nov
Temperature in Boulder in Fall
Over the season highs ease from about 75°F in early September to 41°F by late November.
A typical fall day in Boulder reaches about 58°F and drops to 33°F overnight. The warmest of the three months is September, the coolest November.
How fall really feels in Boulder
Once humidity and wind are folded in, fall brings about 0 days that feel above 90°F and 54 that feel at or below 32°F.
The story in fall is cold — wind chill drags the overnight "feels like" below the raw low.
Boulder weather by month
How the three fall months (September, October and November) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 37° / 14° | 0.9 | 5.7 | 5.5 | 9.5 | 0.0 |
| Feb | 39° / 16° | 1.0 | 6.7 | 7 | 10.4 | 0.0 |
| Mar | 48° / 22° | 2.0 | 8.8 | 7.2 | 11.7 | 1.7 |
| Apr | 54° / 29° | 3.1 | 11.1 | 7.9 | 13 | 3.1 |
| May | 63° / 38° | 4.0 | 14.9 | 3.5 | 14.2 | 4.8 |
| Jun | 74° / 47° | 3.0 | 14.3 | 0.3 | 14.8 | 6.2 |
| Jul | 80° / 53° | 3.0 | 14.8 | 0 | 14.5 | 6.0 |
| Aug | 78° / 52° | 2.8 | 14.9 | 0 | 13.6 | 6.2 |
| Sep | 71° / 44° | 2.1 | 9.7 | 0.9 | 12.3 | 6.8 |
| Oct | 58° / 33° | 1.9 | 7.4 | 3.9 | 10.9 | 4.9 |
| Nov | 46° / 22° | 1.3 | 6.4 | 5.7 | 9.8 | 1.4 |
| Dec | 37° / 15° | 0.9 | 5.3 | 5.4 | 9.2 | 0.0 |
Cloud cover in Fall
The sky is clear or mostly clear about 51% of the time across fall.
Chance of precipitation in Fall
Boulder gets around 5.3 in of rain and snow over 24 wet days across fall. The line is the day-by-day chance of measurable precipitation.
Humidity in Fall
Most of fall feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Fall
Winds average 5 mph across fall.
Sunrise & sunset in Fall
Daylight runs from about 12 h 54 min in early September to 9 h 24 min by late November. The lit band spans sunrise to sunset each day.
Solar energy in Fall
Average shortwave solar energy reaching the ground each day across fall, about 4.2 kWh/m².
Hazard calendar for Boulder
In fall, Boulder overlaps its rainy season season. The full year is below, with each hazard's peak months called out.
Boulder's rainy season runs March–October, when most of the year's rain falls.
Is fall a good time to visit Boulder?
Our two travel scores rate fall for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
fall is a reasonable time to visit Boulder for sightseeing.
What to pack for Boulder in Fall
From fall's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In fall, Boulder sees daytime highs around 58°F and nights near 33°F. Pack a warm layer and a heavy coat. Worth having: rain gear and sun protection. About 24 days see rain.
UV index in Boulder in Fall
Clear-sky midday UV across fall averages around 5 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Boulder peaks around July 13 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 4 | 7 | 6 | 7 | 11 | 11 | 10 | 7 | 5 | 3 | 2 |
| Level | Moderate | Moderate | High | High | Very high | Extreme | Extreme | Very high | Very high | High | Moderate | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Moderate |
| Feb | 4 | Moderate |
| Mar | 7 | High |
| Apr | 6 | High |
| May | 7 | Very high |
| Jun | 11 | Extreme |
| Jul | 11 | Extreme |
| Aug | 10 | Very high |
| Sep | 7 | Very high |
| Oct | 5 | High |
| Nov | 3 | Moderate |
| Dec | 2 | Low |
Air quality in Boulder in Fall
Average fine-particle pollution (PM2.5) through the year — so you can see where fall falls, not just the annual average.
Air quality in Boulder is worst in August — around 21 µg/m³ PM2.5 (moderate), about 1.6× the cleanest month (May, 13 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 17 | 15 | 16 | 13 | 13 | 14 | 14 | 21 | 13 | 15 | 15 | 16 |
| Level | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 17 | Moderate |
| Feb | 15 | Moderate |
| Mar | 16 | Moderate |
| Apr | 13 | Moderate |
| May | 13 | Moderate |
| Jun | 14 | Moderate |
| Jul | 14 | Moderate |
| Aug | 21 | Moderate |
| Sep | 13 | Moderate |
| Oct | 15 | Moderate |
| Nov | 15 | Moderate |
| Dec | 16 | Moderate |
Where is Boulder?
Boulder sits at 40.0°N, 105.3°W, 5,328 ft above sea level, in United States. The nearest listed city is Louisville, 8.1 mi away.
Topography around Boulder
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Boulder.
Within 2 miles, the terrain around Boulder has significant variations in elevation — a maximum elevation change of 1,703 ft around an average of 5,495 ft above sea level; within 10 miles, very significant variations in elevation — a maximum elevation change of 4,147 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 9,623 ft.
The land around Boulder is covered by trees (45%) and artificial surfaces (39%) within 2 miles, grassland (44%) and trees (41%) within 10 miles, and trees (41%) and grassland (34%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Boulder (40.015°, -105.2706°, elevation 5,328 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google.