Issaquah weather in August

In August, Issaquah sees average daytime highs of 74°F and overnight lows near 54°F, with 1.6 in of rain across 5.7 wet days and about 14.1 hours of daylight. It is the 1st-warmest and 11th-wettest month of the year here.

Highs ease over the month, from about 76°F in the first days to 72°F by the end. The sky is clear or mostly clear about 45% of the time in August, and the air most often feels dry.

Daylight stretches from about 14 h 48 min at the start of August to 13 h 18 min by month's end. Set against the rest of the year, August is Issaquah's 1st-clearest and 11th-windiest month. For the whole year in context, see Issaquah's year-round climate.

Daytime high
74°
1st warmest
Overnight low
54°
11th coldest
Rainfall
1.6 in
5.7 wet days
Daylight
14 h 06 min
5:10 AM – 7:15 PM
Cloud cover
45%
1st clearest
Wind
4 mph
11th windiest
Solar energy
5.44 kWh/m²
Travel score
7.9
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 August

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 76°F in the first days to 72°F by the end.

A typical August day in Issaquah reaches about 74°F in the afternoon and slips back to 54°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 65°F and 84°F. Set against its neighbours, August runs on par with July and about 6°F warmer than September.

40°50°60°70°80°151015202531
Avg high (°F)Avg low (°F)
17655
27655
37655
47655
57555
67555
77555
87555
97555
107555
117555
127555
137555
147555
157555
167454
177454
187454
197454
207454
217454
227454
237353
247353
257353
267353
277353
287353
297253
307252
317252

How August really feels in Issaquah

Once humidity and wind are folded in, August averages 0 days that feel above 90°F and 0 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
0
wind chill below the day's low

August sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Issaquah weather by month

How August compares with the rest of the year at a glance. August is the 1st-warmest and 11th-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 August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 45% of the time in August, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 17% of August, with mostly cloudy or overcast conditions the remaining 39%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
16832
26832
36634
46634
56535
66535
76337
86337
96337
106238
116238
126040
136040
146040
156040
166040
176040
186040
196040
206139
216040
226040
236040
246040
255941
265941
275941
285941
295941
305842
315842

Chance of precipitation in August

Any precipitation

Issaquah gets around 1.6 in of rain over 5.7 wet days in August. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 18% and peaks near 26% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%40%151015202531
Rain chance (%)
113
213
313
413
513
614
714
814
915
1015
1116
1216
1316
1417
1517
1618
1718
1818
1919
2020
2120
2221
2321
2422
2523
2623
2724
2824
2925
3025
3126

Humidity in August

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, August lands in the dry band about 61% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)
158375
258375
357385
457385
557385
657385
756386
855396
955396
1055396
1155396
1255396
1356386
1456386
1557376
1658375
1759365
1860355
1962344
2062344
2163334
2265323
2366313
2466313
2568302
2669292
2770282
2872271
2972271
3073261
3174251

Wind in August

Winds average 4 mph in August.

Across August, daily wind ranges from about 4 mph on the calmest days to 4 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
14calm
24calm
34calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm
314calm

Sunrise & sunset in August

DaylightNight

Daylight runs from about 14 h 48 min at the start of August to 13 h 18 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 90 minutes over August. Sunrise moves from 4:50 AM to 5:30 AM, and sunset from 7:39 PM to 6:46 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.84:507:39
214.84:517:37
314.74:527:36
414.74:547:34
514.64:557:33
614.64:567:31
714.54:587:30
814.54:597:28
914.45:007:27
1014.45:027:25
1114.35:037:23
1214.35:047:22
1314.25:067:20
1414.25:077:18
1514.15:087:17
1614.15:107:15
1714.05:117:13
1814.05:127:11
1913.95:147:09
2013.95:157:08
2113.85:177:06
2213.85:187:04
2313.75:197:02
2413.75:217:00
2513.65:226:58
2613.55:236:56
2713.55:256:54
2813.45:266:52
2913.45:276:50
3013.35:296:48
3113.35:306:46

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 5.44 kWh/m².

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 — August's 5.44 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
16.1Intense
26.1Intense
36.0Intense
46.0Intense
56.0Bright
65.9Bright
75.9Bright
85.8Bright
95.8Bright
105.7Bright
115.7Bright
125.7Bright
135.6Bright
145.6Bright
155.5Bright
165.5Bright
175.4Bright
185.4Bright
195.3Bright
205.3Bright
215.3Bright
225.2Bright
235.2Bright
245.1Bright
255.0Bright
265.0Bright
275.0Bright
284.9Bright
294.9Bright
304.8Bright
314.8Bright
Planning a trip in August

Hazard calendar for Issaquah

In seasonPeak

None of Issaquah's seasonal hazards are active in August. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

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 August a good time to visit Issaquah?

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

7.9
Sightseeing
1st-best month of the year
6.3
Beach & pool
1st-best month of the year

August is one of the better times to visit Issaquah for general sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Issaquah in August

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

In August, Issaquah sees daytime highs around 74°F and nights near 54°F. Worth packing: light clothes and sun protection. About 6 days see rain.

light clothessun protection

UV index in Issaquah in August

LowModerateHighVery highExtreme

Clear-sky midday UV in August peaks around 6 — enough to warrant sun protection. 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 August

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where August 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
August 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).