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Monthly climate in Issaquah, Washington, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Issaquah features a warm-summer Mediterranean climate (Csb).Temperatures typically range between 4 °C (39 °F) and 18 °C (65 °F) through the year, but rarely can drop to -12 °C (10 °F) or can rise to as high as 42 °C (108 °F).The average annual precipitation amounts to about 1715 mm (67.5 inches) and receives 172 rainy days on the 1 mm (0.04 inches) threshold annually.Issaquah enjoys an average of 2528 hours of sunshine throughout the year, and daylight varies from 8 hours 29 minutes to 15 hours 53 minutes per day.

Monthly average temperatures in Issaquah, Washington, United States §

The warmest months in Issaquah are June, July and August, with daily mean temperatures ranging from 16 to 18 °C (60 - 65 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from 4 to 5 °C (39 - 40 °F) throughout the day. On average each year, Issaquah experiences 29 days above 25 °C (77.0 °F) and 37 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Issaquah, 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 15°C
(59°F)		 15°C
(60°F)		 24°C
(76°F)		 28°C
(82°F)		 30°C
(86°F)		 42°C
(108°F)		 32°C
(91°F)		 35°C
(94°F)		 32°C
(90°F)		 24°C
(75°F)		 17°C
(64°F)		 14°C
(58°F)
Mean maximum 13°C
(56°F)		 13°C
(55°F)		 18°C
(64°F)		 23°C
(73°F)		 26°C
(80°F)		 30°C
(86°F)		 31°C
(87°F)		 32°C
(90°F)		 28°C
(82°F)		 20°C
(69°F)		 16°C
(61°F)		 12°C
(54°F)
Average high 8°C
(46°F)		 7°C
(45°F)		 11°C
(52°F)		 14°C
(57°F)		 18°C
(64°F)		 20°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
(40°F)		 4°C
(39°F)		 7°C
(44°F)		 9°C
(49°F)		 13°C
(55°F)		 16°C
(60°F)		 18°C
(65°F)		 18°C
(65°F)		 15°C
(60°F)		 10°C
(50°F)		 7°C
(45°F)		 4°C
(40°F)
Average low 2°C
(36°F)		 1°C
(34°F)		 3°C
(37°F)		 5°C
(41°F)		 8°C
(47°F)		 11°C
(52°F)		 13°C
(55°F)		 13°C
(56°F)		 11°C
(52°F)		 6°C
(43°F)		 4°C
(40°F)		 2°C
(36°F)
Mean minimum -6°C
(22°F)		 -6°C
(21°F)		 -2°C
(28°F)		 -0°C
(31°F)		 3°C
(38°F)		 6°C
(44°F)		 9°C
(49°F)		 8°C
(47°F)		 6°C
(43°F)		 -1°C
(31°F)		 -2°C
(28°F)		 -6°C
(22°F)
Minimum -12°C
(11°F)		 -12°C
(10°F)		 -3°C
(26°F)		 -3°C
(27°F)		 1°C
(35°F)		 6°C
(42°F)		 8°C
(47°F)		 7°C
(44°F)		 4°C
(40°F)		 -4°C
(25°F)		 -4°C
(25°F)		 -10°C
(14°F)

Compare climate in Issaquah with other places

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

Monthly average precipitation in Issaquah, Washington, United States §

Issaquah usually has the most precipitation in February, November and December, with an average of 19 rainy days and 229 mm (9.0 inches) of precipitation per month.The driest months in Issaquah are June, July and August. On average, 43 mm (1.7 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Issaquah, 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) 199 (7.9) 234 (9.2) 152 (6.0) 144 (5.7) 85 (3.3) 78 (3.1) 28 (1.1) 23 (0.9) 115 (4.5) 204 (8.1) 217 (8.5) 235 (9.3)
Average precipitation days (≥ 1 mm) 16 20 17 15 14 11 7 5 12 16 19 20

Monthly sunshine hours in Issaquah, Washington, United States §

The sunniest months in Issaquah are June, July and August, when the sun shines an average of 10 hours 45 minutes a day.Least sunny months in Issaquah: January, November and December receive an average of 3 hours 1 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Issaquah, 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 79 111 191 230 295 302 357 328 250 181 110 88
Mean daily daylight hours 8h 55m 10h 16m 11h 57m 13h 40m 15h 9m 15h 53m 15h 28m 14h 9m 12h 29m 10h 47m 9h 16m 8h 29m

Solar UV radiation in Issaquah, Washington, United States §

Issaquah 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, November and December are in the Low exposure category. In these months, the maximum values of the UV index do not exceed 2. For more detailed information, check out our hourly Issaquah UV Index data.

Average daily maximum UV levels by month for Issaquah, 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 2 2