Our verdict
The best time to visit Boulder is September-October
In the height of summer, temperatures in Boulder can reach a maximum of 28℃ (82℉). In the colder months such as December, temperatures usually get down to an average minimum of -8℃ (18℉).
The sun stays up the longest in Boulder in July, so you’ll get the most out of your daytime activities if you visit around this time. The wet season in Boulder falls around May, so if you prefer the dryer weather, you should look to visit in January instead.
Learn everything you need to know (and none of the stuff you don’t) about when to go to Boulder below. Be sure to check out the handy tools we’ve included to help you search for flights and transport, accommodation, and everything else you need to plan and book your trip.
Quick links: Fast facts / Seasons / Average temperatures / Monthly climate / FAQs / Map
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Boulder seasons
Before you continue, it’s important to know when the seasons are in Boulder as they might be different to yours depending on where in the world you’re travelling from. Boulder is in the Northern Hemisphere, so the seasons fall during these months:
| Season | Months |
|---|---|
| Summer | June to August |
| Autumn/fall | September to November |
| Winter | December to February |
| Spring | March to May |
Average temperatures in Boulder
If the temperature is a big factor for you to help you decide when to visit, the chart below shows the average minimum and maximum temperatures in Boulder for each month side-by-side so you can easily see the difference in weather throughout the year. To see the temperatures in both Celsius (°C) and Fahrenheit (°F), hover or tap the shaded boxes on the graph.
Boulder climate by month
If you already have a rough idea about which months you might want to travel, the section below shows a detailed breakdown of the climate in Boulder for each month so you can see if it all suits your wants and needs. Scroll down, or use the quick menu below to jump to your preferred month.
Jump to:
Boulder in January
- Average temperature: -3℃ (27℉)
- Average high temperature: 3℃ (37℉)
- Average low temperature: -7℃ (19℉)
- Average humidity: 68%
- Average sunny days: 22 days
- Average rainfall: 10mm (0") over 4 days
- Average snow days: 6 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in January, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Boulder in February
- Average temperature: -3℃ (26℉)
- Average high temperature: 2℃ (36℉)
- Average low temperature: -8℃ (18℉)
- Average humidity: 71%
- Average sunny days: 16 days
- Average rainfall: 19mm (1") over 4 days
- Average snow days: 10 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in February, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Boulder in March
- Average temperature: 2℃ (36℉)
- Average high temperature: 8℃ (46℉)
- Average low temperature: -3℃ (26℉)
- Average humidity: 61%
- Average sunny days: 17 days
- Average rainfall: 29mm (1") over 9 days
- Average snow days: 6 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in March, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Boulder in April
- Average temperature: 5℃ (42℉)
- Average high temperature: 11℃ (52℉)
- Average low temperature: -1℃ (31℉)
- Average humidity: 59%
- Average sunny days: 13 days
- Average rainfall: 42mm (2") over 12 days
- Average snow days: 5 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in April, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Boulder in May
- Average temperature: 10℃ (50℉)
- Average high temperature: 16℃ (61℉)
- Average low temperature: 4℃ (39℉)
- Average humidity: 58%
- Average sunny days: 11 days
- Average rainfall: 63mm (3") over 18 days
- Average snow days: 2 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in May, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Boulder in June
- Average temperature: 17℃ (63℉)
- Average high temperature: 25℃ (77℉)
- Average low temperature: 10℃ (50℉)
- Average humidity: 45%
- Average sunny days: 15 days
- Average rainfall: 36mm (1") over 13 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in June, make sure you pack a coat or jumper for the evenings, and t-shirts and light gear for the daytime.
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Boulder in July
- Average temperature: 20℃ (67℉)
- Average high temperature: 27℃ (80℉)
- Average low temperature: 13℃ (55℉)
- Average humidity: 48%
- Average sunny days: 10 days
- Average rainfall: 47mm (2") over 17 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in July, make sure you pack t-shirts for the daytime and maybe a light jumper for the evenings as it cools down a bit.
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Boulder in August
- Average temperature: 19℃ (66℉)
- Average high temperature: 26℃ (79℉)
- Average low temperature: 12℃ (53℉)
- Average humidity: 45%
- Average sunny days: 13 days
- Average rainfall: 31mm (1") over 14 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in August, make sure you pack a coat or jumper for the evenings, and t-shirts and light gear for the daytime.
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Boulder in September
- Average temperature: 15℃ (59℉)
- Average high temperature: 22℃ (72℉)
- Average low temperature: 9℃ (48℉)
- Average humidity: 45%
- Average sunny days: 18 days
- Average rainfall: 26mm (1") over 10 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in September, make sure you pack a coat or jumper for the evenings and some light clothes for the daytime.
Boulder in October
- Average temperature: 7℃ (45℉)
- Average high temperature: 14℃ (57℉)
- Average low temperature: 2℃ (35℉)
- Average humidity: 51%
- Average sunny days: 20 days
- Average rainfall: 23mm (1") over 7 days
- Average snow days: 3 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in October, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Boulder in November
- Average temperature: 2℃ (35℉)
- Average high temperature: 8℃ (46℉)
- Average low temperature: -3℃ (26℉)
- Average humidity: 56%
- Average sunny days: 22 days
- Average rainfall: 17mm (1") over 3 days
- Average snow days: 6 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in November, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
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Boulder in December
- Average temperature: -4℃ (26℉)
- Average high temperature: 2℃ (36℉)
- Average low temperature: -8℃ (18℉)
- Average humidity: 65%
- Average sunny days: 22 days
- Average rainfall: 13mm (1") over 4 days
- Average snow days: 7 days
of pure sunshine
of showers or rain
What to pack: If you’re heading to Boulder in December, make sure you pack a thick snow/winter jacket, thermals and some extra layers as it's always very cold.
Add visitor or local insider tips >