Pickering Farm · Photo: Joe Mabel · CC BY-SA 3.0Issaquah has some of the coolest summers among U.S. towns
January mornings start at about 36°. From frosty January to warm July, readings climb 42°. Winters are mild: January nights here are milder than in 83% of U.S. towns. For walks and days out, the stretch from May to September brings highs of 66–77°.
A year in Issaquah at a glance
Each month’s typical high and low, and what it brings.
What stands out about Issaquah’s climate
Compared with towns across the U.S., with Issaquah’s place in Washington beside it.
What a year in Issaquah feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 248 frost-free days a year
In half of years the last 32° night comes by March 13 and the first by November 16. Frost and day counts come from NOAA’s station at Renton Muni Airport, 8 miles from the town’s center, 240 ft lower.
The 2023 USDA map puts Issaquah’s center in zone 9a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 21°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 4 inches of snow a winter
Snow, measured at Snoqualmie Falls, WA, falls mostly in January and December. Precipitation (rain plus melted snow) adds up to 42 inches a year; November is the wettest month and July the driest. Rain or snow falls on about 184 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Issaquah
94% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Renton Muni Airport.
Living with Issaquah’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
248 frost-free days in zone 9a. The last frost comes by Mar 13 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 16.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 36 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Issaquah from natural hazards, earthquakes are the largest share (69%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Issaquah and its neighbors
Every town next door is within a degree of Issaquah in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Issaquah’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Issaquah, WA | 36° | 77° | 42" | 3.6" |
| West Linn, OR | 36° | 81° | 44" | 3.6" |
| Fairfax, CA | 41° | 76° | 38" | 0.0" |
| Nantucket, MA | 26° | 76° | 44" | 25" |
| Brigantine, NJ | 28° | 83° | 45" | 10" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
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°).
A smaller shift than in 85% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Issaquah compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Issaquah’s place among Washington’s.
Issaquah weather by month
Highs, lows and precipitation from NOAA’s grid at Issaquah’s center; snow, wet days and snow on the ground from Snoqualmie Falls, WA. 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" | 0.0" | 18 | 0 | 46° – 56° |
| May | 66° | 47° | 2.4" | 0.0" | 15 | 0 | 52° – 60° |
| June | 70° | 52° | 1.9" | 0.0" | 13 | 0 | 58° – 67° |
| July | 77° | 55° | 0.8" | 0.0" | 7 | 0 | 61° – 70° |
| August | 77° | 55° | 1.0" | 0.0" | 6 | 0 | 62° – 69° |
| September | 71° | 51° | 1.9" | 0.0" | 11 | 0 | 58° – 65° |
| October | 60° | 45° | 4.3" | 0.0" | 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 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 36° to 48°. September is the most reliable, staying within 7°.
Where Issaquah’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Issaquah’s center.
- Snow: Snoqualmie Falls, WA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Renton Muni Airport, 8 miles from the town’s center, 240 ft lower; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Issaquah’s climate
What is the weather like in Issaquah?
A typical July afternoon reaches 77°, a January night drops to 36°, and about 4 inches of snow falls in a normal winter. Milder January nights than 83% of U.S. towns; cooler July afternoons than 98% of U.S. towns.
How cold does it get in Issaquah in winter?
December nights average 35°. About 30 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 36°.
How much snow does Issaquah get?
About 3.6 inches in a normal winter at Snoqualmie Falls, WA, most of it in January and December, with snow on the ground about 3 days a year.
How hot does it get in Issaquah?
July, with a typical high of 77° and a low of 55°. About 4 days a year reach 90° (Renton Muni Airport).
When is the first and last frost in Issaquah?
In half of years the last spring frost (32°) comes by March 13 and the first fall frost by November 16, about 248 frost-free days, at Renton Muni Airport.
What growing zone is Issaquah in?
Zone 9a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 21°.
What is the best time of year to visit Issaquah?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Issaquah getting warmer?
Yes: 1991–2020 averaged 0.9° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 85% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Issaquah.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.