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Monthly climate in Grand Coulee, Washington, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Grand Coulee features a cold semi-arid climate (BSk).Temperatures typically range between -2 °C (28 °F) and 24 °C (75 °F) through the year, but rarely can drop to -24 °C (-11 °F) or can rise to as high as 43 °C (110 °F).The average annual precipitation amounts to about 436 mm (17.2 inches) and receives 81 rainy days on the 1 mm (0.04 inches) threshold annually.Grand Coulee enjoys an average of 3128 hours of sunshine throughout the year, and daylight varies from 8 hours 26 minutes to 15 hours 57 minutes per day.

Monthly average temperatures in Grand Coulee, Washington, United States §

The warmest months in Grand Coulee are June, July and August, with daily mean temperatures ranging from 20 to 24 °C (68 - 75 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from -2 to -2 °C (28 - 29 °F) throughout the day. On average each year, Grand Coulee experiences 71 days above 25 °C (77.0 °F) and 111 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Grand Coulee, Washington, 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 9°C
(49°F)		 11°C
(53°F)		 18°C
(65°F)		 26°C
(78°F)		 31°C
(89°F)		 43°C
(110°F)		 41°C
(107°F)		 39°C
(102°F)		 35°C
(95°F)		 26°C
(78°F)		 16°C
(60°F)		 16°C
(60°F)
Mean maximum 6°C
(43°F)		 8°C
(46°F)		 16°C
(60°F)		 21°C
(71°F)		 29°C
(84°F)		 33°C
(91°F)		 37°C
(99°F)		 37°C
(99°F)		 31°C
(88°F)		 20°C
(69°F)		 14°C
(58°F)		 9°C
(48°F)
Average high 0°C
(33°F)		 2°C
(35°F)		 9°C
(48°F)		 14°C
(57°F)		 21°C
(69°F)		 25°C
(78°F)		 30°C
(87°F)		 30°C
(86°F)		 22°C
(73°F)		 13°C
(56°F)		 6°C
(43°F)		 1°C
(34°F)
Daily mean -2°C
(28°F)		 -2°C
(28°F)		 4°C
(39°F)		 9°C
(48°F)		 15°C
(59°F)		 20°C
(68°F)		 24°C
(75°F)		 23°C
(74°F)		 17°C
(62°F)		 8°C
(48°F)		 3°C
(37°F)		 -2°C
(29°F)
Average low -5°C
(23°F)		 -6°C
(22°F)		 -1°C
(31°F)		 3°C
(38°F)		 9°C
(49°F)		 13°C
(56°F)		 17°C
(62°F)		 16°C
(61°F)		 11°C
(53°F)		 4°C
(40°F)		 -0°C
(32°F)		 -4°C
(25°F)
Mean minimum -16°C
(4°F)		 -13°C
(9°F)		 -8°C
(17°F)		 -2°C
(29°F)		 3°C
(38°F)		 8°C
(46°F)		 12°C
(53°F)		 10°C
(51°F)		 5°C
(41°F)		 -3°C
(27°F)		 -5°C
(23°F)		 -12°C
(11°F)
Minimum -24°C
(-11°F)		 -15°C
(4°F)		 -18°C
(0°F)		 -4°C
(26°F)		 1°C
(34°F)		 6°C
(43°F)		 11°C
(51°F)		 8°C
(46°F)		 2°C
(36°F)		 -7°C
(20°F)		 -9°C
(16°F)		 -19°C
(-2°F)

Compare climate in Grand Coulee with other places

Compare temperature, precipitation, sunshine, UV index in Grand Coulee, Washington, United States with other places around the world.

Monthly average precipitation in Grand Coulee, Washington, United States §

Grand Coulee usually has the most precipitation in January, November and December, with an average of 11 rainy days and 58 mm (2.3 inches) of precipitation per month.The driest months in Grand Coulee are June, July and August. On average, 8 mm (0.3 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Grand Coulee, Washington, 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) 67 (2.6) 47 (1.9) 46 (1.8) 39 (1.6) 37 (1.4) 13 (0.5) 4 (0.1) 8 (0.3) 24 (1.0) 42 (1.7) 51 (2.0) 57 (2.2)
Average precipitation days (≥ 1 mm) 11 9 8 7 7 4 1 2 3 7 11 11

Monthly sunshine hours in Grand Coulee, Washington, United States §

The sunniest months in Grand Coulee are June, July and August, when the sun shines an average of 12 hours 37 minutes a day.Least sunny months in Grand Coulee: January, November and December receive an average of 4 hours 2 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Grand Coulee, Washington, 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 97 170 245 291 355 381 417 363 290 239 153 121
Mean daily daylight hours 8h 52m 10h 15m 11h 57m 13h 41m 15h 11m 15h 57m 15h 31m 14h 11m 12h 30m 10h 46m 9h 13m 8h 26m

Solar UV radiation in Grand Coulee, Washington, United States §

Grand Coulee experiences the highest level of ultraviolet (UV) radiation in June, July and August, when the maximum UV index can reach values of 9 - 9, which corresponds to the Very High 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 Grand Coulee UV Index data.

Average daily maximum UV levels by month for Grand Coulee, Washington, 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) 2 4 5 6 8 9 9 9 7 5 3 2