Plainfield weather in September

In September, Plainfield sees average daytime highs of 74°F and overnight lows near 55°F, with 3.0 in of rain across 8.3 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 7th-wettest month of the year here.

Highs ease over the month, from about 79°F in the first days to 70°F by the end. The sky is clear or mostly clear about 42% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Plainfield's 1st-clearest and 10th-windiest month. For the whole year in context, see Plainfield's year-round climate.

Daytime high
74°
4th warmest
Overnight low
55°
9th coldest
Rainfall
3.0 in
8.3 wet days
Daylight
12 h 18 min
5:39 AM – 5:55 PM
Cloud cover
50%
1st clearest
Wind
7 mph
10th windiest
Solar energy
4.46 kWh/m²
Travel score
7.1
out of 10

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 79°F in the first days to 70°F by the end.

A typical September day in Plainfield reaches about 74°F in the afternoon and slips back to 55°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 64°F and 85°F. Set against its neighbours, September runs about 6°F cooler than August and about 13°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
17961
27960
37960
47860
57859
67859
77758
87758
97758
107657
117657
127656
137556
147556
157555
167455
177455
187454
197354
207353
217253
227252
237252
247152
257151
267051
277050
287050
296950
306949

How September really feels in Plainfield

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.

Plainfield weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 7th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan31° / 17°2.18.15.99.30.0
Feb35° / 20°2.074.610.30.0
Mar47° / 30°2.79.62.911.71.5
Apr59° / 40°4.411.80.913.14.3
May70° / 51°4.612.7014.36.0
Jun79° / 61°4.311.80156.3
Jul83° / 65°3.711.2014.75.9
Aug81° / 63°3.610.5013.76.5
Sep74° / 55°3.08.3012.37.1
Oct62° / 43°3.19.10.110.95.3
Nov47° / 33°2.58.21.29.71.7
Dec36° / 23°2.284.390.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 42% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 15% of September, with mostly cloudy or overcast conditions the remaining 43%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16040
26040
36040
46139
56139
66040
76040
86040
96040
106040
115941
125842
135842
145842
155743
165743
175644
185644
195545
205545
215545
225545
235446
245446
255446
265446
275446
285446
295347
305347

Chance of precipitation in September

Any precipitation

Plainfield gets around 3.0 in of rain over 8.3 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 29% and peaks near 30% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
130
229
329
429
529
629
729
829
929
1029
1129
1229
1329
1429
1529
1629
1729
1829
1929
2028
2128
2228
2328
2428
2528
2628
2728
2828
2928
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 49% of days. Sticky, muggy-or-worse air turns up on roughly 13% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1212723228
2222723217
3242723197
4262822186
5282822175
6302822165
7322821154
8342721144
9362721143
10382620133
11402620132
12422519122
13432519122
14452418111
15472317111
16492317101
17512216101
1853221591
1956211490
2059201380
2160201280
2262191270
2364181170
2466181060
2567171060
266917950
277016950
287216840
297315840
307614730

Wind in September

Winds average 7 mph in September.

Across September, daily wind ranges from about 6 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277light breeze
288light breeze
298light breeze
308light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 hours at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 84 minutes over September. Sunrise moves from 5:23 AM to 5:54 AM, and sunset from 6:22 PM to 5:30 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:236:22
212.95:246:20
312.95:256:18
412.85:266:17
512.85:276:15
612.75:286:13
712.75:296:11
812.75:306:10
912.65:326:08
1012.65:336:06
1112.55:346:04
1212.55:356:03
1312.45:366:01
1412.45:375:59
1512.35:385:57
1612.35:395:55
1712.25:405:54
1812.25:415:52
1912.15:425:50
2012.15:435:48
2112.05:445:46
2212.05:455:45
2311.95:465:43
2411.95:475:41
2511.85:495:39
2611.85:505:37
2711.75:515:36
2811.75:525:34
2911.75:535:32
3011.65:545:30

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 1.65 kWh/m² to a high of 6.3 kWh/m² in June across the year — September's 4.46 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
15.0Bright
25.0Bright
34.9Bright
44.9Bright
54.8Bright
64.8Bright
74.8Bright
84.7Bright
94.7Bright
104.7Bright
114.6Bright
124.6Bright
134.5Bright
144.5Bright
154.5Bright
164.4Bright
174.4Bright
184.3Bright
194.3Bright
204.3Bright
214.2Bright
224.2Bright
234.1Bright
244.1Bright
254.0Bright
264.0Moderate
274.0Moderate
283.9Moderate
293.9Moderate
303.8Moderate
Planning a trip in September

Is September a good time to visit Plainfield?

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

7.1
Sightseeing
1st-best month of the year
5.6
Beach & pool
4th-best month of the year

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

What to pack for Plainfield in September

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

In September, Plainfield sees daytime highs around 74°F and nights near 55°F. Worth packing: light clothes and rain gear. About 8 days see rain.

light clothesrain gear

Sea temperature near Plainfield in September

The nearest coast averages about 68°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 34 mi away) is warmest in August at about 73°F and coldest in February near 36°F.

It's comfortable for a long swim from Jul 13 to Sep 15 — about 2.1 months when the water holds above 68°F.

30°40°50°60°70°80°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°F)Comfort
Jan38Bracing
Feb36Bracing
Mar36Bracing
Apr39Bracing
May45Bracing
Jun57Bracing
Jul70Refreshing
Aug73Refreshing
Sep68Refreshing
Oct58Bracing
Nov49Bracing
Dec42Bracing

UV index in Plainfield in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September 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 Plainfield peaks around June 20 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJun 20UV 9Dec 19UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May7Very high
Jun9Very high
Jul8Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov2Moderate
Dec2Low

Air quality in Plainfield 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 Plainfield is worst in July — around 17 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (October, 9 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodJul 1817 µg/m³Oct 229 µg/m³
PM2.5 (µg/m³)Level
Jan12Moderate
Feb15Moderate
Mar16Moderate
Apr14Moderate
May15Moderate
Jun16Moderate
Jul17Moderate
Aug16Moderate
Sep13Moderate
Oct9Good
Nov10Good
Dec11Good
Location & terrain

Where is Plainfield?

Plainfield sits at 41.6°N, 88.2°W, 617 ft above sea level, in United States. The nearest listed city is Romeoville, 6.2 mi away.

Topography around Plainfield

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

Within 2 miles, the terrain around Plainfield has only modest variations in elevation — a maximum elevation change of 174 ft around an average of 620 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 413 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 751 ft.

The land around Plainfield is covered by trees (24%), grassland (23%) and artificial surfaces (23%) within 2 miles, cropland (27%), grassland (24%) and artificial surfaces (24%) within 10 miles, and cropland (50%) within 50 miles.

2 miles
174 ft
10 miles
413 ft
50 miles
751 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Romeoville 6.2 mi · Crest Hill 7.5 mi · Shorewood 7.5 mi · Lockport 8.1 mi · Oswego 8.7 mi · Bolingbrook 8.7 mi · Joliet 9.3 mi · Montgomery 9.9 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 Plainfield (41.627°, -88.204°, elevation 617 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).