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January Weather in Boulder, United States

Last updated: June 24, 2025

In Boulder, United States, the average temperature in January hovers around -8°C (18°F), with extremes ranging from a chilling -29°C (-20°F) to a relatively mild 3°C (38°F). During this month, expect about 23 mm (0.9 in) of precipitation over approximately 7 days, while the humidity remains notably high at 87%.

January Temperature in Boulder

In January in Boulder, the average temperature is -8°C (18°F), with a maximum that can reach 3°C (38°F) and a minimum that can drop as low as -29°C (-20°F). Be prepared for extremely cold conditions if traveling during this time.

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

The chart illustrates January 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, January typically has an average temperature of -8°C (18°F), with highs reaching up to 3°C (38°F) and lows dropping to around -29°C (-20°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.

January Precipitation in Boulder

In Boulder in January, the total precipitation amount is 23 mm (0.9 in) over a duration of 7 days.

January Precipitation Trends in Boulder

The chart displays monthly precipitation patterns in Boulder, with values for each month alongside January’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how January’s conditions compare to those of other months. In Boulder, January typically receives around 23 mm (0.9 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec2356406892112443943443432
Data source: Precipitation data for January generated using information from the Copernicus Climate Change Service.
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January Humidity in Boulder

In Boulder in January, humidity is 87%. With an average temperature of -8°C (18°F), this humidity feels like a biting chill that seeps into your bones, making it crucial for travelers to bundle up in layers to combat the damp cold and stay comfortable while exploring.

January Average Humidity in Boulder

This chart illustrates the average monthly humidity levels in Boulder, with January’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In January, average humidity in Boulder is approximately 87%, 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 January generated using information from the Copernicus Climate Change Service.

January UV Index in Boulder

In Boulder in January, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in Boulder, you can check the information here.

Maximum UV Index Levels in Boulder for January

The chart shows the monthly maximum UV Index (UVI) for Boulder in January, 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 January, the maximum UV index in Boulder typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34689111098532
Data source: Boulder January 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 January 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 January’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 January’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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