Bainbridge Island weather in September

In September, Bainbridge Island sees average daytime highs of 66°F and overnight lows near 55°F, with 2.4 in of rain across 9 wet days and about 12.4 hours of daylight. It is the 3rd-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 69°F in the first days to 63°F by the end. The sky is clear or mostly clear about 41% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 12 min at the start of September to 11 h 30 min by month's end. Set against the rest of the year, September is Bainbridge Island's 3rd-clearest and 8th-windiest month. For the whole year in context, see Bainbridge Island's year-round climate.

Daytime high
66°
3rd warmest
Overnight low
55°
10th coldest
Rainfall
2.4 in
9 wet days
Daylight
12 h 18 min
5:54 AM – 6:15 PM
Cloud cover
48%
3rd clearest
Wind
5 mph
8th windiest
Solar energy
3.99 kWh/m²
Travel score
6.4
out of 10

Bainbridge Island is city in Kitsap County, Washington, United States.

Density
141/km²
people per km²
Founded
1841

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

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 69°F in the first days to 63°F by the end.

A typical September day in Bainbridge Island reaches about 66°F in the afternoon and slips back to 55°F overnight — a 12°F spread between the day's warmth and the night's chill. On most days the high lands between 60°F and 73°F. Set against its neighbours, September runs about 5°F cooler than August and about 9°F warmer than October.

40°50°60°70°80°151015202530
Avg high (°F)Avg low (°F)
16956
26956
36956
46956
56956
66956
76856
86856
96856
106855
116755
126755
136755
146755
156755
166655
176655
186654
196654
206554
216554
226554
236553
246453
256453
266453
276453
286353
296352
306352

Bainbridge Island weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan46° / 40°6.217.71.98.71.0
Feb48° / 40°4.114.51.49.91.4
Mar51° / 42°4.7170.811.62.1
Apr55° / 45°3.714.80.113.33.1
May61° / 49°2.611.9014.94.8
Jun65° / 53°2.410.3015.75.9
Jul71° / 57°1.36.2015.47.5
Aug72° / 58°1.45.7014.17.7
Sep66° / 55°2.49012.46.4
Oct58° / 49°4.814.9010.63.8
Nov50° / 43°6.917.70.59.11.8
Dec45° / 40°6.617.42.28.30.9

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 41% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 17% of September, with mostly cloudy or overcast conditions the remaining 42%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16238
26238
36238
46337
56337
66337
76337
86337
96139
106040
116040
125941
135842
145743
155743
165644
175644
185644
195545
205545
215545
225446
235545
245545
255545
265545
275446
285446
295446
305347

Chance of precipitation in September

Any precipitation

Bainbridge Island gets around 2.4 in of rain over 9 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 31% and peaks near 33% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
128
228
329
429
529
629
729
829
930
1030
1131
1231
1331
1431
1531
1631
1731
1832
1932
2032
2132
2232
2332
2432
2532
2632
2732
2832
2933
3033

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the dry band about 77% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
169301
269301
370291
471281
571281
672271
773261
874251
974251
1075241
1175241
1276231
1376231
1476231
1577221
1677221
1777221
1878211
1978211
2080200
2180200
2281190
2382180
2482180
2583170
2684160
2785150
2886140
2986140
3087130

Wind in September

Winds average 5 mph in September.

Across September, daily wind ranges from about 5 mph on the calmest days to 6 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
306calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 12 min at the start of September to 11 h 30 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 102 minutes over September. Sunrise moves from 5:33 AM to 6:14 AM, and sunset from 6:46 PM to 5:45 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.25:336:46
213.25:356:44
313.15:366:42
413.05:386:40
513.05:396:38
612.95:406:36
712.95:426:34
812.85:436:32
912.75:456:29
1012.75:466:27
1112.65:476:25
1212.65:496:23
1312.55:506:21
1412.55:516:19
1512.45:536:17
1612.35:546:15
1712.35:566:12
1812.25:576:10
1912.25:586:08
2012.16:006:06
2112.06:016:04
2212.06:036:02
2311.96:046:00
2411.96:055:57
2511.86:075:55
2611.76:085:53
2711.76:105:51
2811.66:115:49
2911.66:135:47
3011.56:145:45

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 3.99 kWh/m².

For context, solar energy here swings from a low near 0.86 kWh/m² to a high of 6.07 kWh/m² in July across the year — September's 3.99 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.7Bright
24.6Bright
34.6Bright
44.5Bright
54.5Bright
64.5Bright
74.4Bright
84.4Bright
94.3Bright
104.3Bright
114.2Bright
124.1Bright
134.1Bright
144.0Bright
154.0Moderate
163.9Moderate
173.9Moderate
183.8Moderate
193.8Moderate
203.7Moderate
213.6Moderate
223.6Moderate
233.5Moderate
243.5Moderate
253.5Moderate
263.4Moderate
273.3Moderate
283.3Moderate
293.2Moderate
303.2Moderate
Planning a trip in September

Hazard calendar for Bainbridge Island

In seasonPeak

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

Bainbridge Island'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 September a good time to visit Bainbridge Island?

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

6.4
Sightseeing
3rd-best month of the year
2.8
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Bainbridge Island for sightseeing.

What to pack for Bainbridge Island in September

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

In September, Bainbridge Island sees daytime highs around 66°F and nights near 55°F. Worth packing: rain gear. About 9 days see rain.

rain gear

Sea temperature near Bainbridge Island in September

The nearest coast averages about 53°F in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 38 mi away) is warmest in August at about 53°F and coldest in February near 46°F.

The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.

45°50°55°JanFebMarAprMayJunJulAugSepOctNovDecbracing
Sea temperature (°F)Comfort
Jan46Bracing
Feb46Bracing
Mar47Bracing
Apr48Bracing
May50Bracing
Jun52Bracing
Jul53Bracing
Aug53Bracing
Sep53Bracing
Oct50Bracing
Nov49Bracing
Dec47Bracing

UV index in Bainbridge Island in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Bainbridge Island 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 18 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 18UV 1
UV index (midday)Level
Jan1Low
Feb1Low
Mar4Moderate
Apr5Moderate
May7High
Jun6High
Jul8Very high
Aug6High
Sep4Moderate
Oct3Moderate
Nov1Low
Dec1Low

Air quality in Bainbridge Island in September

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in Bainbridge Island is worst in August — around 20 µg/m³ PM2.5 (moderate), about 3.1× the cleanest month (December, 6 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodGoodModerateGoodModerateGoodAug 2119 µg/m³Dec 157 µg/m³
PM2.5 (µg/m³)Level
Jan8Good
Feb10Good
Mar12Moderate
Apr12Good
May13Moderate
Jun11Good
Jul10Good
Aug20Moderate
Sep18Moderate
Oct11Good
Nov7Good
Dec6Good
Location & terrain

Where is Bainbridge Island?

Bainbridge Island sits at 47.6°N, 122.5°W, 89 ft above sea level, in United States. The nearest listed city is Bremerton, 6.8 mi away.

Topography around Bainbridge Island

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

Within 2 miles, the terrain around Bainbridge Island has only modest variations in elevation — a maximum elevation change of 453 ft around an average of 144 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 623 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 7,589 ft.

The land around Bainbridge Island is covered by trees (64%) and water (26%) within 2 miles, water (44%) and trees (40%) within 10 miles, and trees (70%) within 50 miles.

2 miles
453 ft
10 miles
623 ft
50 miles
7,589 ft
treesgrasslandartificial surfacesbare terrainwater
September weather nearby: Bremerton 6.8 mi · Silverdale 8.1 mi · Seattle 8.7 mi · Columbia City 12 mi · Shoreline 12 mi · Burien 14 mi · Edmonds 14 mi · Mercer Island 14 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 Bainbridge Island (47.6262°, -122.5212°, elevation 89 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. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. 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).