Issaquah, WA climate
Issaquah has mild winters and pleasant summers. A typical July afternoon reaches 77°, a January night drops to 36°, and about 4 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Issaquah feels like
Winter
Spring
Summer
Fall
Issaquah weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 47° | 36° | 5.8" | 1.5" | 21 | 1 | 37° – 46° |
| February | 50° | 36° | 3.9" | 0.2" | 16 | 0 | 36° – 48° |
| March | 54° | 38° | 4.5" | 0.3" | 20 | 0 | 42° – 51° |
| April | 59° | 41° | 3.5" | 0 | 18 | 0 | 46° – 56° |
| May | 66° | 47° | 2.4" | 0 | 15 | 0 | 52° – 60° |
| June | 70° | 52° | 1.9" | 0 | 13 | 0 | 58° – 67° |
| July | 77° | 55° | 0.8" | 0 | 7 | 0 | 61° – 70° |
| August | 77° | 55° | 1.0" | 0 | 6 | 0 | 62° – 69° |
| September | 71° | 51° | 1.9" | 0 | 11 | 0 | 58° – 65° |
| October | 60° | 45° | 4.3" | 0 | 17 | 0 | 49° – 58° |
| November | 52° | 39° | 6.4" | 0.1" | 21 | 0 | 41° – 50° |
| December | 46° | 35° | 5.9" | 1.5" | 20 | 1 | 36° – 44° |
| Year | 61° | 44° | 42.2" | 3.6" | 184 | 3 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Issaquah
Issaquah gets 42 inches of rain and melted snow a year. November is the wettest month and July the driest. Rain or snow falls on about 184 days a year.
About 248 frost-free days a year
In half of years the last 32° night comes by March 13 and the first one by November 16. That leaves about 248 frost-free days for gardens, longer than 90% of U.S. towns.
Heating and cooling a home in Issaquah
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Issaquah, 94% of that work is heating and 6% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Issaquah and its neighbors
Issaquah borders 2 towns with climate data. January nights across them vary by 0.4°. Sammamish has the coldest January nights (36°) and Bellevue the hottest July afternoons (76°). Issaquah’s January low is 36° and its July high 77°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Issaquah compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Issaquah averaged 0.9° warmer than the 1900s. The biggest change is in January (+2.5°). The shift is smaller than in 78% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Issaquah’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. February swings the most: between 1991 and 2020 its average temperature ranged from 36° to 48°. September is the most reliable, staying within 7°.
Common questions about Issaquah’s climate
What is the coldest month in Issaquah?
December, with a typical high of 46° and a low of 35°.
What is the hottest month in Issaquah?
August, with a typical high of 77° and a low of 55°. About 4 days a year reach 90°.
How much snow does Issaquah get?
About 4 inches in a normal winter, most of it in January.
When is the first frost in Issaquah?
In half of years the first 32° night comes by November 16, and the last spring frost by March 13.
What is the rainiest month in Issaquah?
November, with 6.4 inches of rain and melted snow. The year totals 42 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Issaquah itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Snoqualmie Falls, WA (10 mi, snow) and Renton Municipal Airport, WA (8 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.