Climate and monthly weather forecastBoulder, CO
Climate and monthly weather forecast
The climate of Boulder
Perched on the east side of the Rocky Mountains, Boulder, Colorado, is situated in the mid-latitude steppe of the Köppen climate classification. Its predominate climate is classified as BSk, which indicates cold and semi-arid weather patterns. Boulder endures a fusion of weather conditions across every season, making it a pleasant city to experience a rotation of climates.Throughout the year, the highs in Boulder reach a peak of 80.4°F (26.9°C) in July, followed closely by 79.5°F (26.4°C) in August. On the other end of the spectrum, temperatures plunge to a chilling 19°F (-7.2°C) in January and 18°F (-7.8°C) in February. On average, relative humidity ranges from 45% in the months of June to September to a damp 70% in February. Precipitation is also spread out in the course of the year, with the highest rainfall of 2.48" (63mm) measured in May. During the winter, monthly snowfall can reach up to 7.76" (197mm) in April, offering plenty of opportunities for winter activities.
The daylight hours increase as the year progresses, starting from 9.7 hours in January to eventually coincide with the solstice in June at 15 hours. Following this peak, there is a gradual decrease to the minimum in December at 9.4 hours.
The best time to visit Boulder
For those planning to visit Boulder, the months from May to September provide versatility in terms of weather, daylight, and outdoor activities. In this time period, the temperature skirts between 52.3°F (11.3°C) to a delightful 80.4°F (26.9°C), inducing the landscape to bloom with lushness. With an average highest rainfall of just 2.48" (63mm) in May, the city experiences a dampened heat that gives way to the bliss of summer.The worst time to visit Boulder
Balancing the pleasures of its warm season, Boulder exhibits a bitter cold in the winter months. The harshness of this season, from December to February, is punctuated by low temperatures that dip to a frigid 19°F (-7.2°C) and snowfall that frequently tops up to 5.83" (148mm). Superimposed with reduced daylight hours that hit a low of 9.4 hours, it becomes unappealing for outdoor activities and sightseeing.Spring weather in Boulder
Spring in Boulder sets in with a slight chill, as March typically begins with a high of 46.4°F (8°C), eventually climbing to reach 61°F (16.1°C) by May. The season is marked by an uptick in humidity, with levels hovering around 58% on average. This is often accompanied by the wettest days of the year, with rainfall levels peaking at 2.48" (63mm) in May. Despite this, spring presents an increase in daylight hours, offering ample time for outdoor activities.Summer weather in Boulder
Delightful summer days in Boulder are characterized by temperatures that scale to a high of 80.4°F (26.9°C) in July, sustaining the warmth until August with a high of 79.5°F (26.4°C). While the humidity drops to about 45%, the city experiences lighter rainfall during these months, typically ranging between 1.5" (38mm) and 1.89" (48mm). The generous daylight hours, peaking at 15 hours in June, invite a host of outdoor events and activities.Autumn weather in Boulder
Autumn introduces Boulder to a gentle coolness, as the high temperatures drop from 72.3°F (22.4°C) in September to a milder 57.2°F (14°C) in October. While humidity subtly increases to 51% on average, the area's rainfall continues to decline, settling at 0.91" (23mm) in October. The welcome decrease in heat and the lingering daylight hours still allow for enjoyable outdoor undertakings.Winter weather in Boulder
Winter in Boulder ushers in a shift to cold weather, with December having temperatures between 19°F (-7.2°C) to 35.2°F (1.8°C). The snowfall frequently reaches its peak in this period, with amounts sometimes amounting up to 5.83" (148mm) in February. The plummeting temperatures are accompanied by shorter daylight hours, decreasing to 9.4 hours in December. Despite the unforgiving cold, it becomes a haven for winter sports' enthusiasts.Weather in January
In Boulder, Colorado, January brings the year's chilliest weather. The month commences with colder average temperatures, reaching a high approximately of 36.7°F (2.6°C) and plummeting to lows approximately of 19°F (-7.2°C). Weather in January »Weather in February
Boulder's February weather is marked by an upward push in temperature, making it slightly warmer than January. The increased warmth is paired with amplified snowfall up to 5.83" (148mm). These weather conditions, coupled with longer daylight hours, contribute to a more pleasant ambience when compared to the previous month. Weather in February »Weather in March
March signifies the advent of spring in Boulder, instigating a marked shift in climate. Temperatures start to climb, establishing the basis for the ensuing warmer months. This month receives maximum snowfall of about 6.26" (159mm), marking the last significant flurry before the arrival of summer. Weather in March »Weather in April
With the arrival of April, Boulder embraces the full potential of spring, leaving behind the heavy snowfall of March. This period of the year is typified by a further rise in temperature and more frequent rainfall, tallying at approximately 1.65" (42mm). Weather in April »Weather in May
May denotes the onset of more agreeable conditions in Boulder, as spring starts to give way to the impending summer. Overall, it is characterised by the longest daylight span of the year, warmer temperatures and heightened humidity levels. Weather in May »Weather in June
Boulder warmly welcomes summer with the arrival of June, presenting an overall break from the dampness of May. The city indulges in warm temperatures, longer sunshine hours and lower chances of rain, making the city's outdoor lifestyle much more enticing. Weather in June »Weather in July
July is the peak of summer in Boulder, offering the highest temperatures of the year. The city's atmosphere becomes infused with summer vibes due to high temperatures, hitting highs around 80.4°F (26.9°C) and lows around 55.2°F (12.9°C). Weather in July »Weather in August
In Boulder, August is the last full summer month, characterized by sustained warmth and decreasing rainfall. Though it mirrors much of July's warmth, a slight dip in temperature indicates the upcoming autumn. The wind velocity typically averages around 5.7mph (9.2km/h) in August, ushering in cooler evenings. Weather in August »Weather in September
As Boulder transitions to fall in September, a significant decline in temperature begins. This month provides a respite from the intense summer heat while still providing plenty of sunshine. Snowfall makes a reappearance but only in trace amounts, setting the stage for the colder months ahead. Weather in September »Weather in October
October brings with it cooler temperatures and the full onset of autumn in Boulder. The month is fitting for outdoor activities, with clear skies, optimal visibility, and less intense sunshine. The city's rainfall drops to approximately 0.91" (23mm), just as winter starts making its presence felt with a slight surge in snowfall. Weather in October »Weather in November
Boulder experiences significant transitions in weather during November, with clear signs of the impending winter. Snowfall marginally increases, painting the city in light winter shades, making it a transformational period from autumn to winter. Weather in November »Weather in December
December in Boulder signs off the calendar year with full blown winter. The city welcomes stringent cold, with frequent encounters of snowfall amounting up to approximately 3.94" (100mm). Temperatures plunge to their yearly lows in line with the season, with daylight hours reaching a dwindling stage. Weather in December »Updated: Jul 9, 2024
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
The month with the least rainfall is January, when the rain falls for 4.3 days and typically collects 0.39" (10mm) of precipitation.
In Boulder, during the entire year, the rain falls for 117.3 days and collects up to 14.17" (360mm) of precipitation.
Months with snowfall are January through May, October through December.
In Boulder, during the entire year, snow falls for 44.8 days and aggregates up to 37.01" (940mm) of snow.
January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index.
The most humid month is February, with an average relative humidity of 70%.
With an average of 6.6h of sunshine, February has the least sunshine of the year.
On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts, and the time zone changes from MST to MDT. Daylight Saving Time ends Sunday, November 3. 2024, at 2:00 am, and the time zone reverts from MDT to MST.
April is the month with the most snowfall. Snow falls for 4.9 days and accumulates 7.76" (197mm) of snow.
The month with the most rainfall is May, when the rain falls for 17.5 days and typically aggregates up to 2.48" (63mm) of precipitation.
The months with the lowest humidity in Boulder are June, August and September, with an average relative humidity of 45%.
In Boulder, snow does not fall in June through September.
June has the longest days of the year in Boulder, with an average of 15h and 0min of daylight.
June and July, with an average of 11.7h of sunshine, are months with the most sunshine.
June through August, with an average maximum UV index of 5, are months with the highest UV index.
July is the warmest month, exhibiting average temperatures of 80.4°F (26.9°C) at the peak and 55.2°F (12.9°C) at the base.
With average temperatures fluctuating between a high of 35.2°F (1.8°C) and a low of 18.1°F (-7.7°C), December stands out as the coldest month.
With an average of 9h and 24min of daylight, December has the shortest days of the year.
Average temperature
Boulder, CO
The warmest month (with the highest average high temperature) is July (80.4°F).
The month with the lowest average high temperature is December (35.2°F).
The month with the highest average low temperature is July (55.2°F).
The coldest month (with the lowest average low temperature) is February (18°F).
Average pressure
Boulder, CO
- Average pressure in January:
30.15"Hg - Average pressure in February:
30.08"Hg - Average pressure in March:
30"Hg - Average pressure in April:
29.92"Hg - Average pressure in May:
29.92"Hg - Average pressure in June:
29.92"Hg
- Average pressure in July:
30.01"Hg - Average pressure in August:
30.01"Hg - Average pressure in September:
30.01"Hg - Average pressure in October:
30.03"Hg - Average pressure in November:
30.09"Hg - Average pressure in December:
30.13"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The months with the lowest atmospheric pressure are April, May and June (29.92"Hg).
Average wind speed
Boulder, CO
- Average wind speed in January:
7.3mph - Average wind speed in February:
6.9mph - Average wind speed in March:
6.9mph - Average wind speed in April:
6.6mph - Average wind speed in May:
5.7mph - Average wind speed in June:
6mph
- Average wind speed in July:
5.7mph - Average wind speed in August:
5.7mph - Average wind speed in September:
5.7mph - Average wind speed in October:
6.2mph - Average wind speed in November:
6.8mph - Average wind speed in December:
6.8mph
The windiest month (with the highest average wind speed) is January (7.3mph).
The calmest months (with the lowest average wind speed) are May, July, August and September (5.7mph).
Average humidity
Boulder, CO
The month with the highest relative humidity is February (70%).
The months with the lowest relative humidity are June, August and September (45%).
Average rainfall
Boulder, CO
- Average rainfall in January:
0.39" - Average rainfall in February:
0.75" - Average rainfall in March:
1.14" - Average rainfall in April:
1.65" - Average rainfall in May:
2.48" - Average rainfall in June:
1.5"
- Average rainfall in July:
1.89" - Average rainfall in August:
1.26" - Average rainfall in September:
1.02" - Average rainfall in October:
0.91" - Average rainfall in November:
0.67" - Average rainfall in December:
0.51"
The wettest month (with the highest rainfall) is May (2.48").
The driest month (with the least rainfall) is January (0.39").
Average rainfall days
Boulder, CO
- Average rainfall days in January:
4.3 days - Average rainfall days in February:
4 days - Average rainfall days in March:
9.3 days - Average rainfall days in April:
12.3 days - Average rainfall days in May:
17.5 days - Average rainfall days in June:
13.4 days
- Average rainfall days in July:
17.8 days - Average rainfall days in August:
14.6 days - Average rainfall days in September:
9.9 days - Average rainfall days in October:
7 days - Average rainfall days in November:
3.3 days - Average rainfall days in December:
3.9 days
The month with the highest number of rainy days is July (17.8 days).
The month with the least rainy days is November (3.3 days).
Average snowfall
Boulder, CO
- Average snowfall in January:
2.87" - Average snowfall in February:
5.83" - Average snowfall in March:
6.26" - Average snowfall in April:
7.76" - Average snowfall in May:
1.65" - Average snowfall in June:
0"
The month with the highest snowfall is April (7.76").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days
Boulder, CO
- Average snowfall days in January:
6.3 days - Average snowfall days in February:
10.3 days - Average snowfall days in March:
6.1 days - Average snowfall days in April:
4.9 days - Average snowfall days in May:
1.7 days - Average snowfall days in June:
0 days
- Average snowfall days in July:
0 days - Average snowfall days in August:
0 days - Average snowfall days in September:
0.1 days - Average snowfall days in October:
2.6 days - Average snowfall days in November:
5.6 days - Average snowfall days in December:
7.2 days
The month with the highest number of snowfall days is February (10.3 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight / Average sunshine
Boulder, CO
- Average daylight in January:
9h and 42min - Average daylight in February:
10h and 42min - Average daylight in March:
12h and 0min - Average daylight in April:
13h and 18min - Average daylight in May:
14h and 24min - Average daylight in June:
15h and 0min
- Average daylight in July:
14h and 42min - Average daylight in August:
13h and 42min - Average daylight in September:
12h and 24min - Average daylight in October:
11h and 6min - Average daylight in November:
10h and 0min - Average daylight in December:
9h and 24min
The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in January:
6h and 54min - Average sunshine in February:
6h and 36min - Average sunshine in March:
8h and 42min - Average sunshine in April:
10h and 18min - Average sunshine in May:
10h and 42min - Average sunshine in June:
11h and 42min
- Average sunshine in July:
11h and 42min - Average sunshine in August:
11h and 36min - Average sunshine in September:
10h and 54min - Average sunshine in October:
7h and 18min - Average sunshine in November:
7h and 6min - Average sunshine in December:
6h and 48min
The months with the most sunshine are June and July (Average sunshine: 11h and 42min).
The month with the least sunshine is February (Average sunshine: 6h and 36min).
Average sunshine days
Boulder, CO
- Average sunshine days in January:
22.2 days - Average sunshine days in February:
15.8 days - Average sunshine days in March:
17.1 days - Average sunshine days in April:
13.2 days - Average sunshine days in May:
10.9 days - Average sunshine days in June:
14.3 days
- Average sunshine days in July:
9.9 days - Average sunshine days in August:
12.4 days - Average sunshine days in September:
17.6 days - Average sunshine days in October:
20.2 days - Average sunshine days in November:
21.9 days - Average sunshine days in December:
21.9 days
The month with the most sunshine days is January (22.2 days).
The month with the least sunshine days is July (9.9 days).
Average UV index
Boulder, CO
The months with the highest UV index are June, July and August (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover
Boulder, CO
The months with the most cloud cover are April and May (Cloud cover 28).
The month with the least cloud cover is September (Cloud cover 16).
Average visibility
Boulder, CO
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
