Bellingham weather in September

In September, Bellingham sees average daytime highs of 64°F and overnight lows near 54°F, with 3.2 in of rain across 9.1 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 66°F in the first days to 61°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 18 min at the start of September to 11 h 30 min by month's end. Set against the rest of the year, September is Bellingham's 3rd-clearest and 12th-windiest month. For the whole year in context, see Bellingham's year-round climate.

Daytime high
64°
3rd warmest
Overnight low
54°
10th coldest
Rainfall
3.2 in
9.1 wet days
Daylight
12 h 24 min
5:54 AM – 6:15 PM
Cloud cover
49%
3rd clearest
Wind
5 mph
12th windiest
Solar energy
4.11 kWh/m²
Travel score
5.9
out of 10

Bellingham is city in, and the county seat of, Whatcom County in the State of Washington, United States.

Density
1,084/km²
people per km²
Founded
1852

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 66°F in the first days to 61°F by the end.

A typical September day in Bellingham reaches about 64°F in the afternoon and slips back to 54°F overnight — a 9°F spread between the day's warmth and the night's chill. On most days the high lands between 58°F and 70°F. Set against its neighbours, September runs about 4°F cooler than August and about 8°F warmer than October.

40°50°60°70°80°151015202530
Avg high (°F)Avg low (°F)
16656
26656
36656
46556
56556
66556
76556
86556
96555
106555
116455
126455
136455
146455
156454
166454
176354
186354
196354
206353
216353
226253
236253
246253
256252
266252
276152
286152
296151
306051

How September really feels in Bellingham

Once humidity and wind are folded in, September 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

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

Bellingham 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
Jan44° / 38°8.418.63.28.50.6
Feb46° / 38°5.415.32.89.81.0
Mar49° / 40°6.718.91.911.61.5
Apr53° / 43°4.815.20.113.42.5
May57° / 48°3.411.30154.0
Jun61° / 53°2.59.4015.95.2
Jul66° / 57°1.35.1015.57.1
Aug67° / 58°1.85.3014.27.2
Sep64° / 54°3.29.1012.45.9
Oct56° / 48°6.414.7010.53.3
Nov48° / 41°9.518.81.191.4
Dec44° / 38°8.118.33.38.10.5

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 16% 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 (%)
16139
26139
36139
46139
56238
66238
76238
86238
96139
106040
116040
125941
135941
145842
155842
165743
175743
185644
195644
205644
215545
225545
235545
245545
255545
265545
275545
285446
295347
305248

Chance of precipitation in September

Any precipitation

Bellingham gets around 3.2 in of rain over 9.1 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. The odds climb toward the end of the month.

0%10%20%30%40%151015202530
Rain chance (%)
125
225
326
426
527
627
728
829
930
1030
1131
1232
1333
1433
1533
1633
1733
1833
1933
2033
2133
2233
2333
2433
2532
2632
2732
2832
2932
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 66% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
148484
249474
350464
451454
552444
654424
755414
856404
958393
1059383
1160373
1261363
1362353
1464342
1565332
1666322
1767312
1868302
1970291
2072271
2173261
2274251
2376231
2477221
2580200
2681190
2782180
2884160
2985150
3087130

Wind in September

Winds average 5 mph in September, the calmest month.

Across September, daily wind ranges from about 4 mph on the calmest days to 5 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
15calm
25calm
35calm
45calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 18 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 108 minutes over September. Sunrise moves from 5:32 AM to 6:14 AM, and sunset from 6:47 PM to 5:44 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.35:326:47
213.25:336:45
313.15:356:43
413.15:366:41
513.05:386:39
613.05:396:37
712.95:416:35
812.85:426:32
912.85:436:30
1012.75:456:28
1112.75:466:26
1212.65:486:24
1312.55:496:21
1412.55:516:19
1512.45:526:17
1612.45:546:15
1712.35:556:13
1812.25:576:10
1912.25:586:08
2012.16:006:06
2112.06:016:04
2212.06:036:02
2311.96:045:59
2411.96:055:57
2511.86:075:55
2611.76:085:53
2711.76:105:51
2811.66:115:48
2911.66:135:46
3011.56:145:44

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.11 kWh/m².

For context, solar energy here swings from a low near 0.84 kWh/m² to a high of 6.56 kWh/m² in July across the year — September's 4.11 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.8Bright
24.8Bright
34.8Bright
44.7Bright
54.7Bright
64.6Bright
74.6Bright
84.5Bright
94.5Bright
104.4Bright
114.3Bright
124.3Bright
134.2Bright
144.2Bright
154.1Bright
164.0Bright
174.0Moderate
183.9Moderate
193.9Moderate
203.8Moderate
213.8Moderate
223.7Moderate
233.6Moderate
243.6Moderate
253.5Moderate
263.5Moderate
273.4Moderate
283.4Moderate
293.3Moderate
303.2Moderate
Planning a trip in September

Hazard calendar for Bellingham

In seasonPeak

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

Bellingham'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 Bellingham?

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

5.9
Sightseeing
3rd-best month of the year
1.7
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Bellingham for sightseeing.

What to pack for Bellingham in September

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

In September, Bellingham sees daytime highs around 64°F and nights near 54°F. Worth packing: rain gear. About 9 days see rain.

rain gear

Sea temperature near Bellingham in September

The nearest coast averages about 57°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 19 mi away) is warmest in August at about 60°F and coldest in January near 45°F.

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

45°50°55°60°JanFebMarAprMayJunJulAugSepOctNovDecbracingcool
Sea temperature (°F)Comfort
Jan45Bracing
Feb45Bracing
Mar46Bracing
Apr49Bracing
May53Bracing
Jun56Bracing
Jul59Cool
Aug60Cool
Sep57Bracing
Oct52Bracing
Nov49Bracing
Dec46Bracing

UV index in Bellingham 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 Bellingham 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
Apr4Moderate
May7High
Jun6High
Jul8Very high
Aug6High
Sep4Moderate
Oct3Moderate
Nov1Low
Dec1Low

Air quality in Bellingham 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 Bellingham is worst in September — around 18 µg/m³ PM2.5 (moderate), about 3.2× the cleanest month (December, 6 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodSep 1018 µg/m³Dec 176 µg/m³
PM2.5 (µg/m³)Level
Jan7Good
Feb9Good
Mar12Good
Apr12Good
May12Good
Jun11Good
Jul11Good
Aug18Moderate
Sep18Moderate
Oct12Good
Nov7Good
Dec6Good
Location & terrain

Where is Bellingham?

Bellingham sits at 48.8°N, 122.5°W, 69 ft above sea level, in United States. The nearest listed city is Anacortes, 18 mi away.

Topography around Bellingham

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

Within 2 miles, the terrain around Bellingham has only modest variations in elevation — a maximum elevation change of 666 ft around an average of 102 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,097 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 10,758 ft.

The land around Bellingham is covered by trees (39%), artificial surfaces (29%) and water (23%) within 2 miles, trees (49%) and water (26%) within 10 miles, and trees (51%) and water (32%) within 50 miles.

2 miles
666 ft
10 miles
3,097 ft
50 miles
10,758 ft
treesgrasslandcroplandartificial surfacesbare terrainsnow and icewater
September weather nearby: Anacortes 18 mi · Townline 22 mi · White Rock 23 mi · Abbotsford 23 mi · South Surrey 24 mi · Mount Vernon 24 mi · Langley 25 mi · Cloverdale 27 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 Bellingham (48.7595°, -122.4882°, elevation 69 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).