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Monthly climate in Boulder, Montana, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Boulder features a cold semi-arid climate (BSk).Temperatures typically range between -9 °C (16 °F) and 18 °C (65 °F) through the year, but rarely can drop to -32 °C (-25 °F) or can rise to as high as 34 °C (93 °F).The average annual precipitation amounts to about 627 mm (24.7 inches) and receives 129 rainy days on the 1 mm (0.04 inches) threshold annually.Boulder enjoys an average of 3141 hours of sunshine throughout the year, and daylight varies from 8 hours 39 minutes to 15 hours 42 minutes per day.

Monthly average temperatures in Boulder, Montana, United States §

The warmest months in Boulder are June, July and August, with daily mean temperatures ranging from 14 to 18 °C (57 - 65 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from -9 to -8 °C (16 - 19 °F) throughout the day. On average each year, Boulder experiences 44 days above 25 °C (77.0 °F) and 190 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Boulder, Montana, United States.Generated using Copernicus Climate Change Service information.Data for period from January 2017 to June 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Maximum 3°C
(38°F)		 8°C
(46°F)		 15°C
(59°F)		 22°C
(71°F)		 25°C
(77°F)		 33°C
(92°F)		 34°C
(93°F)		 34°C
(93°F)		 32°C
(91°F)		 25°C
(77°F)		 17°C
(63°F)		 15°C
(59°F)
Mean maximum 3°C
(37°F)		 6°C
(43°F)		 10°C
(51°F)		 18°C
(65°F)		 23°C
(74°F)		 26°C
(79°F)		 31°C
(89°F)		 32°C
(89°F)		 30°C
(87°F)		 20°C
(69°F)		 11°C
(53°F)		 6°C
(43°F)
Average high -4°C
(26°F)		 -4°C
(24°F)		 3°C
(37°F)		 7°C
(45°F)		 14°C
(57°F)		 20°C
(69°F)		 27°C
(80°F)		 26°C
(78°F)		 20°C
(68°F)		 9°C
(49°F)		 3°C
(37°F)		 -3°C
(28°F)
Daily mean -8°C
(18°F)		 -9°C
(16°F)		 -2°C
(28°F)		 1°C
(34°F)		 8°C
(46°F)		 14°C
(57°F)		 18°C
(65°F)		 17°C
(64°F)		 12°C
(54°F)		 3°C
(38°F)		 -3°C
(28°F)		 -8°C
(19°F)
Average low -12°C
(10°F)		 -14°C
(7°F)		 -7°C
(19°F)		 -4°C
(25°F)		 2°C
(36°F)		 7°C
(45°F)		 10°C
(50°F)		 10°C
(50°F)		 5°C
(42°F)		 -2°C
(28°F)		 -7°C
(19°F)		 -12°C
(10°F)
Mean minimum -24°C
(-11°F)		 -27°C
(-16°F)		 -20°C
(-4°F)		 -14°C
(7°F)		 -6°C
(22°F)		 -0°C
(32°F)		 3°C
(38°F)		 4°C
(39°F)		 -4°C
(26°F)		 -14°C
(7°F)		 -17°C
(1°F)		 -23°C
(-10°F)
Minimum -29°C
(-20°F)		 -32°C
(-25°F)		 -30°C
(-21°F)		 -21°C
(-6°F)		 -8°C
(17°F)		 -3°C
(27°F)		 -0°C
(32°F)		 2°C
(37°F)		 -7°C
(19°F)		 -26°C
(-14°F)		 -21°C
(-6°F)		 -28°C
(-17°F)

Compare climate in Boulder with other places

Compare temperature, precipitation, sunshine, UV index in Boulder, Montana, United States with other places around the world.

Monthly average precipitation in Boulder, Montana, United States §

Boulder usually has the most precipitation in April, May and June, with an average of 14 rainy days and 91 mm (3.6 inches) of precipitation per month.The driest months in Boulder are January, November and December. On average, 30 mm (1.2 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Boulder, Montana, United States.Generated using Copernicus Climate Change Service information.Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Average precipitation mm (inches) 23 (0.9) 55 (2.2) 40 (1.6) 68 (2.7) 92 (3.6) 112 (4.4) 44 (1.7) 39 (1.5) 43 (1.7) 44 (1.7) 34 (1.3) 32 (1.3)
Average precipitation days (≥ 1 mm) 7 14 11 13 17 14 10 9 7 10 9 8

Monthly sunshine hours in Boulder, Montana, United States §

The sunniest months in Boulder are June, July and August, when the sun shines an average of 11 hours 53 minutes a day.Least sunny months in Boulder: January, February and December receive an average of 5 hours 33 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Boulder, Montana, United States.Generated using Copernicus Atmosphere Monitoring Service information.Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean monthly sunshine hours 148 178 265 278 302 351 395 347 272 231 190 179
Mean daily daylight hours 9h 4m 10h 21m 11h 57m 13h 36m 15h 0m 15h 42m 15h 19m 14h 3m 12h 28m 10h 50m 9h 24m 8h 39m

Solar UV radiation in Boulder, Montana, United States §

Boulder experiences the highest level of ultraviolet (UV) radiation in June, July and August, when the maximum UV index can reach values of 9 - 11, which corresponds to the Very High / Extreme category of sun exposure.January, November and December are in the Low / Moderate exposure category. In these months, the maximum values of the UV index do not exceed 3. For more detailed information, check out our hourly Boulder UV Index data.

Average daily maximum UV levels by month for Boulder, Montana, United States.Generated using Copernicus Atmosphere Monitoring Service information.Data for period from January 2022 to January 2023.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
UV Index (month maximum) 3 4 6 8 9 11 10 9 8 5 3 2