Galesburg weather in September

In September, Galesburg sees average daytime highs of 76°F and overnight lows near 56°F, with 3.4 in of rain across 8.5 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 80°F in the first days to 71°F by the end. The sky is clear or mostly clear about 46% 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 Galesburg's 1st-clearest and 9th-windiest month. For the whole year in context, see Galesburg's year-round climate.

Daytime high
76°
4th warmest
Overnight low
56°
9th coldest
Rainfall
3.4 in
8.5 wet days
Daylight
12 h 18 min
5:48 AM – 6:04 PM
Cloud cover
47%
1st clearest
Wind
8 mph
9th windiest
Solar energy
4.64 kWh/m²
Travel score
7.2
out of 10

Galesburg is county seat of Knox County, Illinois, United States.

Density
674/km²
people per km²
Founded
1837

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 80°F in the first days to 71°F by the end.

A typical September day in Galesburg reaches about 76°F in the afternoon and slips back to 56°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 65°F and 86°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)
18062
28061
38061
48060
57960
67960
77959
87859
97858
107858
117758
127757
137657
147656
157656
167556
177555
187555
197454
207454
217454
227353
237353
247352
257252
267252
277151
287151
297150
307050

How September really feels in Galesburg

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.

Galesburg 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
Jan32° / 17°2.07.85.29.40.0
Feb36° / 21°2.07.14.310.40.0
Mar49° / 31°2.910.12.211.71.9
Apr61° / 42°4.4120.713.14.7
May71° / 53°4.713.2014.36.1
Jun80° / 63°4.711.6014.96.2
Jul83° / 66°3.59.6014.65.8
Aug82° / 64°3.39.4013.66.5
Sep76° / 56°3.48.5012.37.2
Oct63° / 44°2.98.70.210.95.7
Nov48° / 33°2.67.71.29.72.0
Dec37° / 23°2.17.13.69.10.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 46% 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 40%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16337
26337
36337
46337
56436
66436
76337
86337
96436
106337
116238
126238
136139
146040
156040
165941
175941
185941
195842
205842
215941
225842
235842
245842
255842
265842
275842
285842
295842
305842

Chance of precipitation in September

Any precipitation

Galesburg gets around 3.4 in of rain over 8.5 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 31% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
129
230
330
430
530
630
730
830
931
1031
1131
1231
1331
1431
1531
1630
1730
1830
1929
2028
2128
2227
2327
2427
2526
2626
2726
2826
2926
3025

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 47% of days. Sticky, muggy-or-worse air turns up on roughly 15% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
12123222410
2222422239
3242422218
4262522207
5282521196
6302521186
7322621175
8342520165
9362520154
10372519154
11392419143
12412418143
13432418133
14452317132
15472316122
16482215122
17502215112
18522214111
19552113101
20552113101
2158201291
2260191191
2362191180
2464181170
2565181070
2667171060
276917950
287016950
297116940
307315840

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
127calm
137light breeze
147light 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 5:32 AM to 6:02 AM, and sunset from 6:30 PM to 5:39 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:326:30
212.95:336:28
312.95:356:27
412.85:366:25
512.85:376:23
612.75:386:21
712.75:396:20
812.65:406:18
912.65:416:16
1012.55:426:14
1112.55:436:13
1212.55:446:11
1312.45:456:09
1412.45:466:07
1512.35:476:06
1612.35:486:04
1712.25:496:02
1812.25:506:00
1912.15:515:59
2012.15:525:57
2112.05:535:55
2212.05:545:53
2311.95:555:51
2411.95:565:50
2511.85:575:48
2611.85:585:46
2711.85:595:44
2811.76:005:43
2911.76:015:41
3011.66:025:39

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.64 kWh/m².

For context, solar energy here swings from a low near 1.75 kWh/m² to a high of 6.41 kWh/m² in June across the year — September's 4.64 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.2Bright
25.2Bright
35.1Bright
45.1Bright
55.0Bright
65.0Bright
75.0Bright
84.9Bright
94.9Bright
104.8Bright
114.8Bright
124.8Bright
134.7Bright
144.7Bright
154.6Bright
164.6Bright
174.5Bright
184.5Bright
194.5Bright
204.4Bright
214.4Bright
224.3Bright
234.3Bright
244.3Bright
254.2Bright
264.2Bright
274.1Bright
284.1Bright
294.0Bright
304.0Moderate
Planning a trip in September

Is September a good time to visit Galesburg?

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

7.2
Sightseeing
1st-best month of the year
6.0
Beach & pool
4th-best month of the year

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

What to pack for Galesburg in September

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

In September, Galesburg sees daytime highs around 76°F and nights near 56°F. Worth packing: light clothes, rain gear and sun protection. About 9 days see rain.

light clothesrain gearsun protection

UV index in Galesburg in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Galesburg peaks around June 19 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 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 highHighModerateJun 19UV 9Dec 21UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep7High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Galesburg 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 Galesburg is worst in July — around 16 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (October, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodModerateGoodJul 1915 µg/m³Oct 228 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb13Moderate
Mar13Moderate
Apr11Good
May13Moderate
Jun13Moderate
Jul16Moderate
Aug15Moderate
Sep11Good
Oct8Good
Nov8Good
Dec9Good
Location & terrain

Where is Galesburg?

Galesburg sits at 40.9°N, 90.4°W, 771 ft above sea level, in United States. The nearest listed city is Macomb, 37 mi away.

Topography around Galesburg

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

Within 2 miles, the terrain around Galesburg has only modest variations in elevation — a maximum elevation change of 75 ft around an average of 778 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 259 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 528 ft.

The land around Galesburg is covered by artificial surfaces (31%), trees (26%) and grassland (22%) within 2 miles, cropland (67%) and trees (21%) within 10 miles, and cropland (68%) and trees (21%) within 50 miles.

2 miles
75 ft
10 miles
259 ft
50 miles
528 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Macomb 37 mi · East Moline 39 mi · Moline 39 mi · Burlington 40 mi · Rock Island 40 mi · Bettendorf 40 mi · Davenport 41 mi · North Peoria 44 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 Galesburg (40.9478°, -90.3712°, elevation 771 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).