Issaquah weather in December

In December, Issaquah sees average daytime highs of 44°F and overnight lows near 35°F, with 8.1 in of precipitation across 18.4 wet days and about 8.3 hours of daylight. It is the 12th-warmest and 3rd-wettest month of the year here.

Day-to-day highs hold fairly steady near 44°F through the month. The sky is clear or mostly clear about 13% of the time in December, and the air most often feels dry.

Daylight stretches from about 8 h 30 min at the start of December to 8 h 18 min by month's end. Set against the rest of the year, December is Issaquah's 12th-clearest and 1st-windiest month. For the whole year in context, see Issaquah's year-round climate.

Daytime high
44°
12th warmest
Overnight low
35°
1st coldest
Precipitation
8.1 in
18.4 wet days
Daylight
8 h 18 min
7:57 AM – 4:12 PM
Cloud cover
77%
12th clearest
Wind
6 mph
1st windiest
Solar energy
0.9 kWh/m²
Travel score
0.6
out of 10

Issaquah is city in King County, Washington, United States.

Density
1,222/km²
people per km²
Founded
1892

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 44°F through the month.

A typical December day in Issaquah reaches about 44°F in the afternoon and slips back to 35°F overnight — a 9°F spread between the day's warmth and the night's chill. On most days the high lands between 38°F and 50°F. Set against its neighbours, December runs about 5°F cooler than November and on par with January.

20°30°40°50°60°151015202531
Avg high (°F)Avg low (°F)
14535
24535
34535
44535
54535
64535
74435
84435
94435
104435
114435
124435
134435
144435
154435
164435
174435
184435
194435
204435
214435
224435
234435
244435
254435
264435
274434
284434
294434
304434
314434

How December really feels in Issaquah

Once humidity and wind are folded in, December averages 0 days that feel above 90°F and 31 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
0
heat index over the day's high
Days feeling ≤ 32°F
31
wind chill below the day's low

The story in December is cold — wind chill drags the overnight "feels like" below the raw low.

Issaquah weather by month

How December compares with the rest of the year at a glance. December is the 12th-warmest and 3rd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan45° / 35°8.318.73.68.70.8
Feb48° / 36°5.815.52.69.91.5
Mar52° / 37°6.518.71.811.62.2
Apr57° / 41°5.416.50.213.33.4
May63° / 46°3.812.8014.95.1
Jun67° / 50°3.211.4015.75.9
Jul74° / 54°1.36.5015.47.7
Aug74° / 54°1.65.7014.17.9
Sep68° / 49°3.49012.46.6
Oct58° / 43°6.615.1010.63.9
Nov49° / 38°9.018.719.11.6
Dec44° / 35°8.118.43.48.30.6

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 13% of the time in December, the cloudiest month of the year.

Beyond those clear spells, partly cloudy skies cover about 8% of December, with mostly cloudy or overcast conditions the remaining 79%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
12575
22575
32575
42575
52377
62377
72377
82278
92278
102179
112179
121981
131981
141882
151783
161783
171783
181882
191981
201981
212080
222080
232080
242179
252179
262278
272278
282278
292377
302377
312476

Chance of precipitation in December

Any precipitationSnow

Issaquah gets around 8.1 in of rain and snow over 18.4 wet days in December. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 61% and peaks near 64% on the wettest days, and about 3 days bring snow.

0%20%40%60%151015202531
Rain chance (%)Snow chance (%)
1598
2598
3598
4598
5598
6598
7598
8608
9608
10618
11618
12629
13639
14639
156410
166410
176411
186311
196312
206313
216213
226214
236114
246114
256014
266015
276015
286015
296015
306015
316015

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

Most of December feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, December lands in the dry band about 100% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)
1100
2100
3100
4100
5100
6100
7100
8100
9100
10100
11100
12100
13100
14100
15100
16100
17100
18100
19100
20100
21100
22100
23100
24100
25100
26100
27100
28100
29100
30100
31100

Wind in December

Winds average 6 mph in December, the windiest month of the year.

Across December, daily wind ranges from about 6 mph on the calmest days to 6 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
96calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
176calm
186calm
196calm
206calm
216calm
226calm
236calm
246calm
256calm
266calm
276calm
286calm
296calm
306calm
316calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 8 h 30 min at the start of December to 8 h 18 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 12 minutes over December. Sunrise moves from 7:42 AM to 8:03 AM, and sunset from 4:14 PM to 4:20 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
18.57:424:14
28.57:434:13
38.57:454:13
48.47:464:12
58.47:474:12
68.47:484:12
78.47:494:12
88.47:504:12
98.37:514:11
108.37:524:11
118.37:534:11
128.37:544:11
138.37:544:11
148.37:554:12
158.37:564:12
168.37:574:12
178.27:574:12
188.27:584:12
198.27:594:13
208.27:594:13
218.28:004:14
228.28:004:14
238.28:014:15
248.28:014:15
258.28:014:16
268.28:024:16
278.28:024:17
288.38:024:18
298.38:024:18
308.38:034:19
318.38:034:20

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 0.9 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 0.9 kWh/m² to a high of 6.18 kWh/m² in July across the year — December's 0.9 kWh/m² sits near the bottom.

00.511.52151015202531
Solar energy (kWh/m²)Level
11.0Dim
21.0Dim
31.0Dim
40.9Dim
50.9Dim
60.9Dim
70.9Dim
80.9Dim
90.9Dim
100.9Dim
110.9Dim
120.9Dim
130.8Dim
140.8Dim
150.8Dim
160.8Dim
170.8Dim
180.8Dim
190.8Dim
200.8Dim
210.8Dim
220.9Dim
230.9Dim
240.9Dim
250.9Dim
260.9Dim
270.9Dim
280.9Dim
290.9Dim
300.9Dim
310.9Dim
Planning a trip in December

Hazard calendar for Issaquah

In seasonPeak

In December, Issaquah sits inside its rainy season season. The full year is below, with each hazard's peak months called out.

Issaquah's rainy season runs October–April, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is December a good time to visit Issaquah?

Our two travel scores rate December for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

0.6
Sightseeing
12th-best month of the year
0.0
Beach & pool
8th-best month of the year

December is a weaker month for outdoor sightseeing in Issaquah.

What to pack for Issaquah in December

From December's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In December, Issaquah sees daytime highs around 44°F and nights near 35°F. Pack a warm layer and rain gear. Worth having: a heavy coat. About 18 days see rain.

a warm layerrain geara heavy coat

UV index in Issaquah in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 1. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Issaquah peaks around July 17 at about 8 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near December 17 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 7 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 17UV 8Dec 17UV 1
UV index (midday)Level
Jan1Low
Feb1Low
Mar4Moderate
Apr5Moderate
May7High
Jun6High
Jul8Very high
Aug6High
Sep4Moderate
Oct3Moderate
Nov1Low
Dec1Low

Air quality in Issaquah in December

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where December falls, not just the annual average.

Air quality in Issaquah is worst in September — around 22 µg/m³ PM2.5 (moderate), about 3.4× the cleanest month (December, 7 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodGoodModerateGoodSep 1322 µg/m³Dec 177 µg/m³
PM2.5 (µg/m³)Level
Jan8Good
Feb9Good
Mar12Moderate
Apr12Good
May11Good
Jun10Good
Jul10Good
Aug18Moderate
Sep22Moderate
Oct12Good
Nov8Good
Dec7Good
Location & terrain

Where is Issaquah?

Issaquah sits at 47.5°N, 122.0°W, 108 ft above sea level, in United States. The nearest listed city is West Lake Sammamish, 4.3 mi away.

Topography around Issaquah

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Issaquah.

Within 2 miles, the terrain around Issaquah has large variations in elevation — a maximum elevation change of 1,998 ft around an average of 512 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,002 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 14,413 ft.

The land around Issaquah is covered by trees (78%) within 2 miles, trees (77%) within 10 miles, and trees (76%) within 50 miles.

2 miles
1,998 ft
10 miles
3,002 ft
50 miles
14,413 ft
treesgrasslandartificial surfacesbare terrainwater
December weather nearby: West Lake Sammamish 4.3 mi · City of Sammamish 5.0 mi · Sammamish 8.1 mi · Fairwood 8.1 mi · Renton 9.3 mi · Mercer Island 9.3 mi · Maple Valley 9.3 mi · Bellevue 9.3 mi

United States travel facts

Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 100% of US
price level, 2025
GDP per capita
$90,027
2025
Happiness
6.8 / 10
World Happiness, 2025
Safe drinking water
98%
of population, 2024
Homicide rate
5.8
per 100k, 2023
Road deaths
12.7
per 100k/yr, 2019
Income group
High
World Bank
Religion
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Issaquah (47.5301°, -122.0326°, elevation 108 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).