Sterling weather in September

In September, Sterling sees average daytime highs of 75°F and overnight lows near 55°F, with 3.4 in of rain across 8.3 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 5th-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 44% 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 Sterling's 1st-clearest and 9th-windiest month. For the whole year in context, see Sterling's year-round climate.

Daytime high
75°
4th warmest
Overnight low
55°
9th coldest
Rainfall
3.4 in
8.3 wet days
Daylight
12 h 18 min
5:45 AM – 6:01 PM
Cloud cover
49%
1st clearest
Wind
8 mph
9th windiest
Solar energy
4.51 kWh/m²
Travel score
7.1
out of 10

Sterling is city in Whiteside County, Illinois, United States.

Density
978/km²
people per km²
Founded
1838

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 79°F in the first days to 70°F by the end.

A typical September day in Sterling reaches about 75°F in the afternoon and slips back to 55°F overnight — a 20°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)
18061
28060
37960
47960
57959
67859
77858
87858
97858
107757
117757
127656
137656
147656
157555
167555
177455
187454
197454
207353
217353
227353
237252
247252
257151
267151
277150
287050
297050
306949

How September really feels in Sterling

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.

Sterling weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan30° / 15°1.97.65.19.30.0
Feb35° / 19°1.96.74.210.30.0
Mar48° / 30°2.69.42.411.71.7
Apr60° / 41°4.311.50.813.14.6
May71° / 52°4.713.2014.36.0
Jun80° / 62°4.5120156.3
Jul83° / 65°3.710.1014.76.0
Aug81° / 63°3.39.1013.76.7
Sep75° / 55°3.48.3012.37.1
Oct62° / 43°2.98.50.210.95.5
Nov47° / 32°2.57.71.39.61.7
Dec35° / 22°2.27.5490.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 44% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 14% of September, with mostly cloudy or overcast conditions the remaining 42%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16139
26238
36238
46337
56337
66337
76436
86337
96337
106238
116139
126040
136040
145941
155842
165743
175644
185644
195644
205545
215545
225545
235545
245545
255545
265545
275545
285545
295545
305545

Chance of precipitation in September

Any precipitation

Sterling gets around 3.4 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 28% and peaks near 30% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
128
228
328
428
528
628
729
829
929
1029
1129
1229
1330
1430
1530
1630
1729
1829
1929
2028
2128
2228
2328
2427
2527
2627
2727
2826
2926
3026

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 50% of days. Sticky, muggy-or-worse air turns up on roughly 14% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1222720229
2232820209
3252819198
4272919187
5292919177
6312918166
7332818155
8352818145
9372717144
10392717134
11412617133
12432517123
13452516123
14472416112
15492315112
16502215112
17532214101
18542114101
1957201391
2058201291
2161191181
2263181180
2366171070
2467171060
256916960
267115950
277115950
287414840
297414840
307713730

Wind in September

Winds average 8 mph in September.

Across September, daily wind ranges from about 7 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (mph)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127light breeze
137light breeze
148light breeze
158light breeze
168light breeze
178light breeze
188light breeze
198light breeze
208light breeze
218light breeze
228light breeze
238light breeze
248light breeze
258light breeze
268light breeze
278light 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 5:29 AM to 6:00 AM, and sunset from 6:28 PM to 5:36 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:296:28
212.95:306:26
312.95:316:25
412.85:326:23
512.85:336:21
612.85:346:19
712.75:356:18
812.75:366:16
912.65:376:14
1012.65:386:12
1112.55:406:10
1212.55:416:09
1312.45:426:07
1412.45:436:05
1512.35:446:03
1612.35:456:01
1712.25:466:00
1812.25:475:58
1912.15:485:56
2012.15:495:54
2112.05:505:52
2212.05:515:51
2311.95:525:49
2411.95:535:47
2511.85:545:45
2611.85:565:43
2711.75:575:42
2811.75:585:40
2911.75:595:38
3011.66:005:36

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.51 kWh/m².

For context, solar energy here swings from a low near 1.71 kWh/m² to a high of 6.34 kWh/m² in June across the year — September's 4.51 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.1Bright
25.0Bright
35.0Bright
45.0Bright
54.9Bright
64.9Bright
74.8Bright
84.8Bright
94.8Bright
104.7Bright
114.7Bright
124.6Bright
134.6Bright
144.5Bright
154.5Bright
164.5Bright
174.4Bright
184.4Bright
194.3Bright
204.3Bright
214.2Bright
224.2Bright
234.2Bright
244.1Bright
254.1Bright
264.0Bright
274.0Moderate
284.0Moderate
293.9Moderate
303.9Moderate
Planning a trip in September

Is September a good time to visit Sterling?

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
5.8
Beach & pool
4th-best month of the year

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

What to pack for Sterling in September

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

In September, Sterling sees daytime highs around 75°F and nights near 55°F. Worth packing: light clothes, rain gear and sun protection. About 8 days see rain.

light clothesrain gearsun protection

UV index in Sterling 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 Sterling peaks around June 18 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 18UV 9Dec 19UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun9Very high
Jul8Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Sterling 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 Sterling is worst in July — around 15 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (October, 7 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodModerateGoodJul 1915 µg/m³Oct 227 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb13Moderate
Mar13Moderate
Apr11Good
May13Moderate
Jun13Moderate
Jul15Moderate
Aug14Moderate
Sep11Good
Oct7Good
Nov8Good
Dec9Good
Location & terrain

Where is Sterling?

Sterling sits at 41.8°N, 89.7°W, 659 ft above sea level, in United States. The nearest listed city is Dixon, 12 mi away.

Topography around Sterling

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

Within 2 miles, the terrain around Sterling has only modest variations in elevation — a maximum elevation change of 121 ft around an average of 656 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 295 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 830 ft.

The land around Sterling is covered by trees (28%) and artificial surfaces (28%) within 2 miles, cropland (81%) within 10 miles, and cropland (77%) within 50 miles.

2 miles
121 ft
10 miles
295 ft
50 miles
830 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Dixon 12 mi · Clinton 25 mi · Freeport 35 mi · East Moline 43 mi · Rockford 45 mi · Bettendorf 46 mi · Moline 47 mi · Davenport 49 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 Sterling (41.7886°, -89.6962°, elevation 659 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).