August weather forecast
Boulder, CO

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The old building of the University of Colorado in Boulder, Colorado
The old building of the University of Colorado in Boulder, Colorado

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. September will see a further decrease in temperature, and the advent of the year's cooler half. Hence, August is the perfect month soaking up last bits of summer before autumn sets in.

Temperature

Boulder marks the onset of August with an average high-temperature of a still warm 79.5°F (26.4°C), a subtle shift from July's 80.4°F (26.9°C). Throughout August, Boulder braces for a considerable drop from daytime highs, with an average low-temperature of 54.1°F (12.3°C).

Humidity

The months with the lowest humidity in Boulder are June, August and September, with an average relative humidity of 45%.

Rainfall

In Boulder, during August, the rain falls for 14.6 days and regularly aggregates up to 1.26" (32mm) of precipitation. Throughout the year, in Boulder, there are 117.3 rainfall days, and 14.17" (360mm) of precipitation is accumulated.

Snowfall

In Boulder, snow does not fall in June through September.

Daylight

In Boulder, the average length of the day in August is 13h and 42min.
On the first day of the month, sunrise is at 6:00 am and sunset at 8:14 pm. On the last day of August, in Boulder, Colorado, sunrise is at 6:28 am and sunset at 7:33 pm MDT.

Sunshine

In Boulder, the average sunshine in August is 11.6h.

UV index

June through August, with an average maximum UV index of 5, are months with the highest UV index in Boulder. A UV Index of 3 to 5 symbolizes a medium health hazard from unprotected exposure to Sun's UV rays for the average person.
Note: In August, the maximum UV index of 5 suggests this advice:
Take precautions - Protection against sunburn is recommended. The intensity of the Sun's UV radiation during midday suggests reducing time spent outdoors. For minimizing sun-related eye damage, always choose sunglasses with UVA and UVB coverage.
Updated: Feb 10, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What are the temperatures in Boulder in August?

Boulder in August has an average high-temperature of 79.5°F (26.4°C) and an average low-temperature of 54.1°F (12.3°C).

What is the least humid month in Boulder?

The months with the lowest humidity are June, August and September, with an average relative humidity of 45%.

What is the average humidity in August in Boulder?

In Boulder, the average relative humidity in August is 45%.

How many days does it rain in August in Boulder?

In Boulder, Colorado, in August, during 14.6 rainfall days, 1.26" (32mm) of precipitation is typically accumulated.

When it does not snow in Boulder?

In Boulder, Colorado, snow does not fall in June through September.

How many hours of daylight does Boulder have in August?

The average day length in August in Boulder, Colorado, is 13h and 42min.

When are sunrise and sunset in August in Boulder?

On the first day of August in Boulder, Colorado, sunrise is at 6:00 am and sunset at 8:14 pm. On the last day of the month, sunrise is at 6:28 am and sunset at 7:33 pm MDT.

How many hours of sunshine does Boulder have in August?

The average sunshine duration in August in Boulder, Colorado, is 11.6h.

What is the month with the highest UV index in Boulder?

The months with the highest UV index are June through August, with an average maximum UV index of 5.

What is the UV index intensity in August in Boulder?

In August, the average daily maximum UV index in Boulder is 5. A UV Index value of 3 to 5 symbolizes a moderate vulnerability from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in August
Boulder, CO

Average temperature in August - Boulder, CO
  • Average high temperature in August: 79.5°F

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).

  • Average low temperature in August: 54.1°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 in August
Boulder, CO

Average pressure in August - Boulder, CO
  • Average pressure in August: 30.01"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 in August
Boulder, CO

Average wind speed in August - Boulder, CO
  • Average wind speed in August: 5.7mph

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 in August
Boulder, CO

Average humidity in August - Boulder, CO
  • Average humidity in August: 45%

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 in August
Boulder, CO

Average rainfall in August - Boulder, CO
  • Average rainfall in August: 1.26"

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 in August
Boulder, CO

Average rainfall days in August - Boulder, CO
  • Average rainfall days in August: 14.6 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 in August
Boulder, CO

Average snowfall in August - Boulder, CO
  • Average snowfall in August: 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 in August
Boulder, CO

Average snowfall days in August - Boulder, CO
  • Average snowfall days in August: 0 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 in August /
Average sunshine in August
Boulder, CO

Average daylight in August / Average sunshine in August - Boulder, CO
  • Average daylight in August: 13h and 4min

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 August: 11h and 4min

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 in August
Boulder, CO

Average sunshine days in August - Boulder, CO
  • Average sunshine days in August: 12.4 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 in August
Boulder, CO

Average UV index in August - Boulder, CO
  • Average UV index in August: 5

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 in August
Boulder, CO

Average cloud cover in August - Boulder, CO
  • Average cloud cover in August: 18

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 in August
Boulder, CO

Average visibility in August - Boulder, CO
  • Average visibility in August: 6mi

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).

Boulder, Colorado, USA

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