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Best time to visit Boulder, CO, USA

Our verdict

The best time to visit Boulder is September-October

Boulder is a place lots of people visit almost all year round, but if you’re looking for the best time to go, September-October is definitely the time you should visit. This is based on a number of factors such as the weather, cost of flights and accommodation, peak travel periods and more.

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.

Warmest month

July

Least rainfall

January

Most daylight

July

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:

SeasonMonths
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:

JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC

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
22 days
of pure sunshine
4 days
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.


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
16 days
of pure sunshine
4 days
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.


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
17 days
of pure sunshine
9 days
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.


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
13 days
of pure sunshine
12 days
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.


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
11 days
of pure sunshine
18 days
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.


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
15 days
of pure sunshine
13 days
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.


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
10 days
of pure sunshine
17 days
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.


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
13 days
of pure sunshine
14 days
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.


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
18 days
of pure sunshine
10 days
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
20 days
of pure sunshine
7 days
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.


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
22 days
of pure sunshine
3 days
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.


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
22 days
of pure sunshine
4 days
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.


Top FAQs

The hottest month of the year in Boulder is usually July, where temperatures tend to rise to around 27℃ (80℉) in the middle of the day or early afternoon.
The month with the least amount of rain in Boulder is generally around January. The dry season often coincides with cooler weather, so you should check the temperatures in January first to make sure it’s still a good time to go.
The rainiest time of year in Boulder is generally around May, although the wetter season can sometimes extend a few months either side of May too.
If you want to get the most out of your time visiting Boulder, or if you're just afraid of the dark, the days in July are usually the longest between sunrise and sunset.

Boulder map