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Monthly climate in Union, Washington, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Union features a warm-summer Mediterranean climate (Csb).Temperatures typically range between 5 °C (41 °F) and 19 °C (66 °F) through the year, but rarely can drop to -5 °C (23 °F) or can rise to as high as 39 °C (102 °F).The average annual precipitation amounts to about 1587 mm (62.5 inches) and receives 147 rainy days on the 1 mm (0.04 inches) threshold annually.Union enjoys an average of 2633 hours of sunshine throughout the year, and daylight varies from 8 hours 30 minutes to 15 hours 52 minutes per day.

Monthly average temperatures in Union, Washington, United States §

The warmest months in Union are July, August and September, with daily mean temperatures ranging from 16 to 19 °C (61 - 66 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from 5 to 5 °C (41 - 42 °F) throughout the day. On average each year, Union experiences 28 days above 25 °C (77.0 °F) and 9 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Union, 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 13°C
(55°F)		 13°C
(56°F)		 21°C
(70°F)		 25°C
(77°F)		 30°C
(86°F)		 39°C
(102°F)		 33°C
(91°F)		 33°C
(93°F)		 30°C
(87°F)		 24°C
(75°F)		 16°C
(61°F)		 13°C
(55°F)
Mean maximum 11°C
(53°F)		 12°C
(53°F)		 17°C
(62°F)		 21°C
(70°F)		 25°C
(78°F)		 30°C
(87°F)		 30°C
(87°F)		 32°C
(90°F)		 27°C
(81°F)		 20°C
(67°F)		 15°C
(60°F)		 12°C
(53°F)
Average high 7°C
(46°F)		 7°C
(45°F)		 10°C
(51°F)		 13°C
(57°F)		 18°C
(64°F)		 21°C
(69°F)		 24°C
(75°F)		 24°C
(76°F)		 20°C
(69°F)		 14°C
(58°F)		 10°C
(51°F)		 7°C
(45°F)
Daily mean 5°C
(42°F)		 5°C
(41°F)		 7°C
(45°F)		 10°C
(49°F)		 13°C
(56°F)		 16°C
(61°F)		 19°C
(66°F)		 19°C
(66°F)		 16°C
(61°F)		 11°C
(52°F)		 8°C
(47°F)		 5°C
(42°F)
Average low 4°C
(39°F)		 2°C
(37°F)		 4°C
(40°F)		 6°C
(43°F)		 10°C
(49°F)		 12°C
(54°F)		 14°C
(57°F)		 14°C
(58°F)		 13°C
(55°F)		 8°C
(47°F)		 6°C
(43°F)		 4°C
(39°F)
Mean minimum -1°C
(31°F)		 -3°C
(27°F)		 0°C
(33°F)		 2°C
(36°F)		 6°C
(43°F)		 8°C
(47°F)		 11°C
(53°F)		 11°C
(53°F)		 9°C
(48°F)		 4°C
(39°F)		 1°C
(35°F)		 -1°C
(30°F)
Minimum -4°C
(25°F)		 -5°C
(23°F)		 -1°C
(31°F)		 0°C
(33°F)		 4°C
(40°F)		 7°C
(44°F)		 10°C
(51°F)		 10°C
(50°F)		 7°C
(45°F)		 1°C
(35°F)		 -0°C
(32°F)		 -5°C
(23°F)

Compare climate in Union with other places

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

Monthly average precipitation in Union, Washington, United States §

Union usually has the most precipitation in January, November and December, with an average of 18 rainy days and 250 mm (9.8 inches) of precipitation per month.The driest months in Union are June, July and August. On average, 24 mm (1.0 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Union, 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) 256 (10.1) 171 (6.7) 148 (5.8) 124 (4.9) 60 (2.4) 49 (1.9) 9 (0.4) 14 (0.6) 95 (3.7) 168 (6.6) 243 (9.6) 250 (9.9)
Average precipitation days (≥ 1 mm) 18 17 16 14 9 7 1 3 10 14 18 20

Monthly sunshine hours in Union, Washington, United States §

The sunniest months in Union are June, July and August, when the sun shines an average of 10 hours 58 minutes a day.Least sunny months in Union: January, November and December receive an average of 3 hours 15 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Union, 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 82 128 208 230 299 317 362 330 256 199 120 96
Mean daily daylight hours 8h 56m 10h 17m 11h 57m 13h 39m 15h 7m 15h 52m 15h 27m 14h 8m 12h 29m 10h 47m 9h 17m 8h 30m

Solar UV radiation in Union, Washington, United States §

Union experiences the highest level of ultraviolet (UV) radiation in June, July and August, when the maximum UV index can reach values of 8 - 9, which corresponds to the Very High category of sun exposure.January, February 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 Union UV Index data.

Average daily maximum UV levels by month for Union, 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 3 5 6 8 9 9 8 7 5 3 2