Forest Grove weather in September

In September, Forest Grove sees average daytime highs of 74°F and overnight lows near 53°F, with 1.7 in of rain across 6 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 78°F in the first days to 70°F by the end. The sky is clear or mostly clear about 48% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 06 min at the start of September to 11 h 30 min by month's end. Set against the rest of the year, September is Forest Grove's 3rd-clearest and 9th-windiest month. For the whole year in context, see Forest Grove's year-round climate.

Daytime high
74°
3rd warmest
Overnight low
53°
10th coldest
Rainfall
1.7 in
6 wet days
Daylight
12 h 18 min
5:57 AM – 6:16 PM
Cloud cover
42%
3rd clearest
Wind
5 mph
9th windiest
Solar energy
4.46 kWh/m²
Travel score
7.7
out of 10

Forest Grove is city in Oregon, USA.

Density
1,608/km²
people per km²
Founded
1840

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 78°F in the first days to 70°F by the end.

A typical September day in Forest Grove reaches about 74°F in the afternoon and slips back to 53°F overnight — a 21°F spread between the day's warmth and the night's chill. On most days the high lands between 64°F and 86°F. Set against its neighbours, September runs about 6°F cooler than August and about 12°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
17855
27855
37855
47755
57755
67755
77754
87654
97654
107654
117654
127554
137553
147553
157453
167453
177453
187353
197352
207352
217352
227252
237251
247151
257151
267151
277051
287050
296950
306950

How September really feels in Forest Grove

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.

Forest Grove 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° / 36°6.817.11.98.91.0
Feb49° / 37°5.214.21.610.11.8
Mar54° / 39°5.917.30.911.62.7
Apr59° / 42°4.515.60.113.23.8
May66° / 47°2.710.6014.75.9
Jun72° / 52°1.67.2015.47.1
Jul80° / 56°0.42.2015.18.2
Aug80° / 57°0.52.5013.98.1
Sep74° / 53°1.76012.37.7
Oct62° / 46°4.211.5010.75.1
Nov51° / 40°7.017.30.59.32.0
Dec45° / 36°8.017.52.38.60.8

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 48% 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 37%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17129
27129
37030
47030
56931
66832
76733
86634
96535
106436
116337
126238
136139
146238
156139
166139
176139
186040
196040
206040
216139
226139
236139
246139
256139
266139
276139
286139
296040
305941

Chance of precipitation in September

Any precipitation

Forest Grove gets around 1.7 in of rain over 6 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 21% and peaks near 27% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%40%151015202530
Rain chance (%)
113
214
314
415
515
616
717
818
918
1019
1120
1221
1321
1421
1522
1622
1722
1822
1922
2022
2123
2223
2323
2423
2523
2624
2724
2825
2926
3027

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 87% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
185150
285150
385150
485150
585150
686140
786140
886140
986140
1085150
1185150
1285150
1385150
1485150
1586140
1686140
1785141
1885141
1986131
2086131
2187121
2287121
2388111
2488111
2589101
269091
279091
289181
299181
309271

Wind in September

Winds average 5 mph in September.

Across September, daily wind ranges from about 5 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
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
305calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 06 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 96 minutes over September. Sunrise moves from 5:38 AM to 6:15 AM, and sunset from 6:46 PM to 5:48 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.15:386:46
213.15:406:44
313.05:416:42
413.05:426:40
512.95:436:38
612.95:456:36
712.85:466:34
812.75:476:32
912.75:486:30
1012.65:506:28
1112.65:516:26
1212.55:526:24
1312.55:546:22
1412.45:556:20
1512.45:566:18
1612.35:576:16
1712.35:596:14
1812.26:006:12
1912.26:016:10
2012.16:026:08
2112.06:046:06
2212.06:056:04
2311.96:066:02
2411.96:086:00
2511.86:095:58
2611.86:105:56
2711.76:115:54
2811.76:135:52
2911.66:145:50
3011.56:155:48

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.46 kWh/m².

For context, solar energy here swings from a low near 1.03 kWh/m² to a high of 6.77 kWh/m² in July across the year — September's 4.46 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.2Bright
25.1Bright
35.1Bright
45.0Bright
55.0Bright
64.9Bright
74.9Bright
84.8Bright
94.8Bright
104.7Bright
114.7Bright
124.6Bright
134.6Bright
144.5Bright
154.4Bright
164.4Bright
174.3Bright
184.3Bright
194.2Bright
204.2Bright
214.1Bright
224.1Bright
234.0Bright
244.0Moderate
253.9Moderate
263.8Moderate
273.8Moderate
283.7Moderate
293.6Moderate
303.6Moderate
Planning a trip in September

Hazard calendar for Forest Grove

In seasonPeak

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

Forest Grove'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 Forest Grove?

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

7.7
Sightseeing
3rd-best month of the year
6.0
Beach & pool
3rd-best month of the year

September is one of the better times to visit Forest Grove for general sightseeing.

What to pack for Forest Grove in September

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

In September, Forest Grove sees daytime highs around 74°F and nights near 53°F. Worth packing: light clothes. About 6 days see rain.

light clothes

Sea temperature near Forest Grove in September

The nearest coast averages about 58°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 59°F and coldest in February near 49°F.

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

50°55°60°JanFebMarAprMayJunJulAugSepOctNovDecbracingcool
Sea temperature (°F)Comfort
Jan50Bracing
Feb49Bracing
Mar50Bracing
Apr51Bracing
May54Bracing
Jun57Bracing
Jul58Bracing
Aug59Bracing
Sep58Bracing
Oct55Bracing
Nov53Bracing
Dec50Bracing

UV index in Forest Grove in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 5 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Forest Grove peaks around July 17 at about 8 (very high) — sunscreen, a hat and midday shade are essential. 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 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateVery highVery highHighModerateLowJul 17UV 8Dec 17UV 1
UV index (midday)Level
Jan1Low
Feb2Low
Mar4Moderate
Apr5High
May8Very high
Jun7High
Jul8Very high
Aug7High
Sep5Moderate
Oct3Moderate
Nov1Low
Dec1Low

Air quality in Forest Grove 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 Forest Grove is worst in September — around 22 µg/m³ PM2.5 (moderate), about 3.0× the cleanest month (January, 7 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodSep 1621 µg/m³Jan 117 µg/m³
PM2.5 (µg/m³)Level
Jan7Good
Feb9Good
Mar11Good
Apr11Good
May10Good
Jun9Good
Jul8Good
Aug13Moderate
Sep22Moderate
Oct14Moderate
Nov9Good
Dec7Good
Location & terrain

Where is Forest Grove?

Forest Grove sits at 45.5°N, 123.1°W, 203 ft above sea level, in United States. The nearest listed city is Hillsboro, 5.6 mi away.

Topography around Forest Grove

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

Within 2 miles, the terrain around Forest Grove has only modest variations in elevation — a maximum elevation change of 331 ft around an average of 187 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,303 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,245 ft.

The land around Forest Grove is covered by trees (33%), grassland (24%) and cropland (24%) within 2 miles, trees (56%) and cropland (20%) within 10 miles, and trees (72%) within 50 miles.

2 miles
331 ft
10 miles
2,303 ft
50 miles
4,245 ft
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Hillsboro 5.6 mi · Aloha 12 mi · Bethany 12 mi · Beaverton 15 mi · Newberg 17 mi · Sherwood 17 mi · Tigard 17 mi · Tualatin 19 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 Forest Grove (45.5198°, -123.1107°, elevation 203 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).