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August Weather in Boulder, United States

Last updated: June 24, 2025

In August, the average temperature in Boulder, United States hovers around 17°C (64°F). Expect a minimum of 2°C (37°F) and a maximum reaching 34°C (93°F). During this time, you'll encounter about 39 mm (1.5 in) of precipitation over 9 days, contributing to an average humidity level of 71%. Stay prepared for the varied climate!

August Temperature in Boulder

In August in Boulder, the average temperature is 17°C (64°F). The maximum can reach 34°C (93°F), and the minimum can be as low as 2°C (37°F). It's advisable to pack layers to comfortably enjoy your time exploring the diverse weather conditions.

August Weather in Boulder: Daily Temperature Highs, Lows, and Averages

The chart illustrates August temperature patterns in Boulder, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Boulder, August typically has an average temperature of 17°C (64°F), with highs reaching up to 34°C (93°F) and lows dropping to around 2°C (37°F).
JanFebMarAprMayJunJulAugSepOctNovDec181528344657656354382718
Data source: Temperature data for Boulder generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

August Precipitation in Boulder

In Boulder in August, the precipitation amount is 39 mm (1.5 in) spread over 9 days.

August Precipitation Trends in Boulder

The chart displays monthly precipitation patterns in Boulder, with values for each month alongside August’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how August’s conditions compare to those of other months. In Boulder, August typically receives around 39 mm (1.5 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec2356406892112443943443432
Data source: Precipitation data for August generated using information from the Copernicus Climate Change Service.
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August Humidity in Boulder

In Boulder in August humidity is 71%. With an average temperature of 17°C (64°F), this humidity feels like a warm, enveloping embrace that can make travel feel a bit sticky, yet still pleasant as you explore the sights with a gentle sheen of perspiration.

August Average Humidity in Boulder

This chart illustrates the average monthly humidity levels in Boulder, with August’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In August, average humidity in Boulder is approximately 71%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec87%88%83%78%76%78%77%71%68%72%84%91%
Data source: Humidity data for August generated using information from the Copernicus Climate Change Service.

August UV Index in Boulder

In Boulder in August, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Boulder.

Maximum UV Index Levels in Boulder for August

The chart shows the monthly maximum UV Index (UVI) for Boulder in August, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In August, the maximum UV index in Boulder typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34689111098532
Data source: Boulder August UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How August Weather in Boulder Compares to Other Months

Weather in Boulder varies notably across the year, with each month offering distinct climate conditions. This page compares August’s weather to other months in Boulder, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Boulder, showing how August’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-8°C (18°F)23 mm (0.9 inches)87%moderate
February Weather-9°C (16°F)55 mm (2.2 inches)88%moderate
March Weather-2°C (28°F)40 mm (1.6 inches)83%high
April Weather1°C (34°F)68 mm (2.7 inches)78%very high
May Weather8°C (46°F)92 mm (3.6 inches)76%very high
June Weather14°C (57°F)112 mm (4.4 inches)78%extreme
July Weather18°C (65°F)44 mm (1.7 inches)77%very high
August Weather17°C (64°F)39 mm (1.5 inches)71%very high
September Weather12°C (54°F)43 mm (1.7 inches)68%very high
October Weather3°C (38°F)44 mm (1.7 inches)72%moderate
November Weather-3°C (28°F)34 mm (1.3 inches)84%moderate
December Weather-8°C (19°F)32 mm (1.3 inches)90%low

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