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Monthly climate in Longmont, Colorado, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Longmont features a cold semi-arid climate (BSk).Temperatures typically range between -1 °C (30 °F) and 23 °C (75 °F) through the year, but rarely can drop to -25 °C (-12 °F) or can rise to as high as 38 °C (100 °F).The average annual precipitation amounts to about 494 mm (19.5 inches) and receives 83 rainy days on the 1 mm (0.04 inches) threshold annually.Longmont enjoys an average of 3502 hours of sunshine throughout the year, and daylight varies from 9 hours 20 minutes to 14 hours 59 minutes per day.

Monthly average temperatures in Longmont, Colorado, United States §

The warmest months in Longmont are June, July and August, with daily mean temperatures ranging from 20 to 23 °C (69 - 75 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from -1 to 0 °C (30 - 33 °F) throughout the day. On average each year, Longmont experiences 102 days above 25 °C (77.0 °F) and 131 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Longmont, Colorado, 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 17°C
(63°F)		 25°C
(77°F)		 27°C
(80°F)		 29°C
(85°F)		 31°C
(88°F)		 38°C
(100°F)		 38°C
(100°F)		 36°C
(97°F)		 37°C
(98°F)		 29°C
(85°F)		 25°C
(78°F)		 22°C
(72°F)
Mean maximum 14°C
(57°F)		 19°C
(66°F)		 23°C
(74°F)		 27°C
(81°F)		 30°C
(86°F)		 33°C
(91°F)		 37°C
(98°F)		 35°C
(95°F)		 36°C
(97°F)		 28°C
(83°F)		 23°C
(74°F)		 16°C
(62°F)
Average high 6°C
(43°F)		 6°C
(43°F)		 13°C
(55°F)		 17°C
(62°F)		 21°C
(69°F)		 28°C
(83°F)		 31°C
(89°F)		 30°C
(87°F)		 27°C
(82°F)		 17°C
(63°F)		 12°C
(55°F)		 8°C
(46°F)
Daily mean -1°C
(30°F)		 -1°C
(30°F)		 5°C
(40°F)		 9°C
(48°F)		 13°C
(56°F)		 20°C
(69°F)		 23°C
(75°F)		 22°C
(73°F)		 19°C
(66°F)		 9°C
(49°F)		 4°C
(40°F)		 0°C
(33°F)
Average low -7°C
(20°F)		 -7°C
(19°F)		 -2°C
(28°F)		 1°C
(35°F)		 7°C
(44°F)		 12°C
(54°F)		 16°C
(61°F)		 15°C
(59°F)		 11°C
(52°F)		 3°C
(37°F)		 -2°C
(29°F)		 -5°C
(23°F)
Mean minimum -18°C
(0°F)		 -20°C
(-3°F)		 -13°C
(8°F)		 -8°C
(19°F)		 0°C
(33°F)		 7°C
(45°F)		 11°C
(53°F)		 12°C
(53°F)		 4°C
(40°F)		 -10°C
(14°F)		 -9°C
(17°F)		 -13°C
(9°F)
Minimum -24°C
(-12°F)		 -25°C
(-12°F)		 -23°C
(-9°F)		 -12°C
(11°F)		 -4°C
(25°F)		 6°C
(43°F)		 10°C
(50°F)		 11°C
(51°F)		 -0°C
(32°F)		 -19°C
(-2°F)		 -12°C
(10°F)		 -16°C
(3°F)

Compare climate in Longmont with other places

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

Monthly average precipitation in Longmont, Colorado, United States §

Longmont usually has the most precipitation in March, April and May, with an average of 11 rainy days and 77 mm (3.0 inches) of precipitation per month.The driest months in Longmont are January, November and December. On average, 19 mm (0.8 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Longmont, Colorado, 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) 19 (0.8) 26 (1.0) 56 (2.2) 55 (2.2) 119 (4.7) 42 (1.6) 31 (1.2) 43 (1.7) 27 (1.1) 38 (1.5) 23 (0.9) 15 (0.6)
Average precipitation days (≥ 1 mm) 4 6 9 10 14 8 7 6 5 6 5 3

Monthly sunshine hours in Longmont, Colorado, United States §

The sunniest months in Longmont are June, July and August, when the sun shines an average of 12 hours 1 minutes a day.Least sunny months in Longmont: January, February and December receive an average of 7 hours 13 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Longmont, Colorado, 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 185 234 285 300 326 373 381 351 306 272 248 237
Mean daily daylight hours 9h 39m 10h 40m 11h 58m 13h 18m 14h 25m 14h 59m 14h 40m 13h 40m 12h 24m 11h 4m 9h 55m 9h 20m

Solar UV radiation in Longmont, Colorado, United States §

Longmont experiences the highest level of ultraviolet (UV) radiation in April, June and July, when the maximum UV index can reach values of 11 - 12, which corresponds to the Extreme category of sun exposure.January, November and December are in the Moderate exposure category. In these months, the maximum values of the UV index do not exceed 4. For more detailed information, check out our hourly Longmont UV Index data.

Average daily maximum UV levels by month for Longmont, Colorado, 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) 4 6 8 11 11 12 12 11 9 6 4 3