Best time to visit Boulder
The best time to visit Boulder is June and August–September, judged on twenty years of weather records and the events worth going for.
Boulder, Colorado, United States
°C
mm
- Average daily high and low
- Precipitation
- Good month
- Best month
- Made good or best by an event
| Month | Average daily high | Average daily low | Precipitation | Verdict |
|---|---|---|---|---|
| January | 2.7 °C / 37 °F | -9.8 °C / 14 °F | 24 mm / 0.9 in | neither best nor good |
| February | 3.4 °C / 38 °F | -9.3 °C / 15 °F | 32 mm / 1.3 in | neither best nor good |
| March | 9.1 °C / 48 °F | -4.9 °C / 23 °F | 50 mm / 2 in | neither best nor good |
| April | 12.5 °C / 55 °F | -1.4 °C / 29 °F | 68 mm / 2.7 in | neither best nor good |
| May | 16.9 °C / 62 °F | 3.5 °C / 38 °F | 111 mm / 4.4 in | good month |
| June | 24.6 °C / 76 °F | 9.3 °C / 49 °F | 67 mm / 2.6 in | best month |
| July | 27.1 °C / 81 °F | 12.5 °C / 55 °F | 77 mm / 3 in | good month |
| August | 26.4 °C / 80 °F | 11.8 °C / 53 °F | 63 mm / 2.5 in | best month |
| September | 22.9 °C / 73 °F | 7.8 °C / 46 °F | 49 mm / 1.9 in | best month |
| October | 15.3 °C / 60 °F | 1.3 °C / 34 °F | 45 mm / 1.8 in | good month |
| November | 9.2 °C / 49 °F | -4.4 °C / 24 °F | 27 mm / 1.1 in | neither best nor good |
| December | 3.6 °C / 38 °F | -8.9 °C / 16 °F | 29 mm / 1.1 in | neither best nor good |
Good and best months depend on more than temperature, rain and events. How they are chosen
Each activity on this page has its own good and best months, rated on twenty years of daily weather records. Which measures count, and how much, depends on the activity: humidity for exploring outdoors, wind for the beach, hiking and skiing, snow for skiing alone. Between them, the activities are rated on:
- Daytime highs
- Night-time lows
- How warm it feels
- Humidity
- How much of the day is sunny
- Hours of daylight
- Monthly rainfall
- How many days it rains
- Days of heavy rain
- Wind
- Snowfall and days with snow
- Major events, such as festivals
The chart shows the good and best months for exploring outdoors.
The event icon marks a month that an event lifts to good or best, such as a festival or a natural spectacle. Choose “Weather only” in the toolbar to rate the months on weather alone.
Best months by activity
Exploring outdoors
Mild days and nights, mostly dry and bright. The default for 'when should I go'.
- JJanuary: neither
- FFebruary: neither
- MMarch: neither
- AApril: neither
- MMay: good
- JJune: best
- JJuly: good
- AAugust: best
- SSeptember: best
- OOctober: good
- NNovember: neither
- DDecember: neither
- Best
- June, August–September
- Good
- May, July, October
Why these months
May · good
In its favour: feels like (high) 15.3 °C / 60 °F, share of daylight that is sunny 87%, average daily high 16.9 °C / 62 °F, precipitation 111 mm / 4.4 in, relative humidity 63%, days with heavy rain 3.5 days.
Against: wet days 15.6 days, average daily low 3.5 °C / 38 °F.
June · best
In its favour: feels like (high) 24 °C / 75 °F, average daily high 24.6 °C / 76 °F, share of daylight that is sunny 89%, precipitation 67 mm / 2.6 in, days with heavy rain 1.5 days, relative humidity 56%, average daily low 9.3 °C / 49 °F.
Against: wet days 13.6 days.
July · good
In its favour: feels like (high) 27.4 °C / 81 °F, share of daylight that is sunny 91%, precipitation 77 mm / 3 in, average daily high 27.1 °C / 81 °F, days with heavy rain 1.8 days, average daily low 12.5 °C / 55 °F, relative humidity 57%.
Against: wet days 16.1 days.
August · best
In its favour: feels like (high) 26 °C / 79 °F, share of daylight that is sunny 93%, precipitation 63 mm / 2.5 in, average daily high 26.4 °C / 80 °F, days with heavy rain 1.4 days, average daily low 11.8 °C / 53 °F, relative humidity 56%.
Against: wet days 12.8 days.
September · best
In its favour: feels like (high) 21.1 °C / 70 °F, average daily high 22.9 °C / 73 °F, precipitation 49 mm / 1.9 in, share of daylight that is sunny 91%, days with heavy rain 1.2 days, wet days 8.7 days, relative humidity 55%, average daily low 7.8 °C / 46 °F.
October · good
In its favour: precipitation 45 mm / 1.8 in, share of daylight that is sunny 90%, average daily high 15.3 °C / 60 °F, days with heavy rain 1.3 days, wet days 7.2 days, relative humidity 57%.
Against: feels like (high) 12 °C / 54 °F, average daily low 1.3 °C / 34 °F.
Hiking and trekking
Cool enough to climb in, dry enough to enjoy, long enough days.
- JJanuary: neither
- FFebruary: neither
- MMarch: good
- AApril: best
- MMay: good
- JJune: best
- JJuly: neither
- AAugust: good
- SSeptember: best
- OOctober: best
- NNovember: good
- DDecember: neither
- Best
- April, June, September–October
- Good
- March, May, August, November
Why these months
March · good
In its favour: precipitation 50 mm / 2 in, average daily high 9.1 °C / 48 °F, days with heavy rain 1.1 days, wet days 8.7 days, share of daylight that is sunny 90%, daylight per day 12 h, wind (daily max) 15 km/h / 9 mph, feels like (high) 5.7 °C / 42 °F.
Against: average daily low -4.9 °C / 23 °F.
April · best
In its favour: average daily high 12.5 °C / 55 °F, precipitation 68 mm / 2.7 in, days with heavy rain 1.7 days, share of daylight that is sunny 87%, daylight per day 13.3 h, wet days 10.4 days, feels like (high) 9.7 °C / 49 °F, wind (daily max) 15 km/h / 9 mph.
Against: average daily low -1.4 °C / 29 °F.
May · good
In its favour: average daily high 16.9 °C / 62 °F, precipitation 111 mm / 4.4 in, feels like (high) 15.3 °C / 60 °F, share of daylight that is sunny 87%, daylight per day 14.4 h, average daily low 3.5 °C / 38 °F, days with heavy rain 3.5 days, wind (daily max) 14 km/h / 9 mph.
Against: wet days 15.6 days.
June · best
In its favour: precipitation 67 mm / 2.6 in, average daily high 24.6 °C / 76 °F, days with heavy rain 1.5 days, average daily low 9.3 °C / 49 °F, share of daylight that is sunny 89%, daylight per day 15 h, feels like (high) 24 °C / 75 °F, wind (daily max) 14 km/h / 8 mph.
Against: wet days 13.6 days.
August · good
In its favour: precipitation 63 mm / 2.5 in, days with heavy rain 1.4 days, average daily low 11.8 °C / 53 °F, share of daylight that is sunny 93%, daylight per day 13.7 h, wind (daily max) 13 km/h / 8 mph, feels like (high) 26 °C / 79 °F.
Against: average daily high 26.4 °C / 80 °F, wet days 12.8 days.
September · best
In its favour: average daily high 22.9 °C / 73 °F, precipitation 49 mm / 1.9 in, days with heavy rain 1.2 days, wet days 8.7 days, feels like (high) 21.1 °C / 70 °F, average daily low 7.8 °C / 46 °F, share of daylight that is sunny 91%, daylight per day 12.4 h, wind (daily max) 13 km/h / 8 mph.
October · best
In its favour: average daily high 15.3 °C / 60 °F, precipitation 45 mm / 1.8 in, wet days 7.2 days, days with heavy rain 1.3 days, feels like (high) 12 °C / 54 °F, share of daylight that is sunny 90%, daylight per day 11.1 h, average daily low 1.3 °C / 34 °F, wind (daily max) 14 km/h / 8 mph.
November · good
In its favour: precipitation 27 mm / 1.1 in, average daily high 9.2 °C / 49 °F, wet days 5.8 days, days with heavy rain 0.6 days, share of daylight that is sunny 90%, wind (daily max) 14 km/h / 9 mph.
Against: average daily low -4.4 °C / 24 °F, feels like (high) 5.4 °C / 42 °F, daylight per day 10 h.
An activity is listed only where it applies: skiing at ski destinations, beach and swimming at beach destinations. The nearest ski area is Eldora, 27 km away.
Weather averages
Monthly averages over twenty years, 2006–2025. Highs, lows and precipitation are in the chart at the top.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels like (high) | -1.2 °C | -0.4 °C | 5.7 °C | 9.7 °C | 15.3 °C | 24 °C | 27.4 °C | 26 °C | 21.1 °C | 12 °C | 5.4 °C | -0.3 °C |
| Days with heavy rain | 0.3 days | 0.3 days | 1.1 days | 1.7 days | 3.5 days | 1.5 days | 1.8 days | 1.4 days | 1.2 days | 1.3 days | 0.6 days | 0.6 days |
| Time rain usually falls | 9 am | 9 pm | 7 pm | 4 pm | 4 pm | 3 pm | 4 pm | 4 pm | 4 pm | 8 pm | 10 pm | 10 pm |
| Sunshine per day | 8.7 h | 9.5 h | 10.7 h | 11.6 h | 12.6 h | 13.4 h | 13.3 h | 12.7 h | 11.3 h | 10 h | 9 h | 8.1 h |
| Relative humidity | 65% | 64% | 59% | 58% | 63% | 56% | 57% | 56% | 55% | 57% | 59% | 63% |
Air quality
Averaged over a shorter period (2022–2025) than the twenty-year averages above, and not counted towards good or best months.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Air pollution (PM2.5) 2022–2025 | 9.6 µg/m³ | 9.7 µg/m³ | 9 µg/m³ | 9.2 µg/m³ | 9.1 µg/m³ | 7.9 µg/m³ | 9 µg/m³ | 7.9 µg/m³ | 6.3 µg/m³ | 5.3 µg/m³ | 6.7 µg/m³ | 7.2 µg/m³ |
| Air pollution (PM2.5, daily peak) 2022–2025 | 17.7 µg/m³ | 17.2 µg/m³ | 15.2 µg/m³ | 15.2 µg/m³ | 14.5 µg/m³ | 12.4 µg/m³ | 14.8 µg/m³ | 11.8 µg/m³ | 10.3 µg/m³ | 9 µg/m³ | 11.8 µg/m³ | 13.2 µg/m³ |
- Good 15 µg/m³ or less
- Fair 15 to 25 µg/m³
- Moderate 25 to 37.5 µg/m³
- Poor 37.5 to 50 µg/m³
- Very poor 50 to 75 µg/m³
- Extremely poor over 75 µg/m³
Each figure is compared with the World Health Organization's guideline for a day's air, 15 µg/m³ or less, and with its interim targets above that. The words are ours: the WHO does not name its steps. The figures are modelled monthly averages, so single days can be well above them. The daily peak is the average of each day's highest hour, shaded on the same scale.