Quincy weather in September

In September, Quincy sees average daytime highs of 78°F and overnight lows near 58°F, with 3.3 in of rain across 7.4 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 82°F in the first days to 73°F by the end. The sky is clear or mostly clear about 49% of the time in September, and the air most often feels dry.

Daylight stretches from about 12 h 54 min at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Quincy's 1st-clearest and 10th-windiest month. For the whole year in context, see Quincy's year-round climate.

Daytime high
78°
4th warmest
Overnight low
58°
9th coldest
Rainfall
3.3 in
7.4 wet days
Daylight
12 h 18 min
5:52 AM – 6:08 PM
Cloud cover
45%
1st clearest
Wind
7 mph
10th windiest
Solar energy
4.77 kWh/m²
Travel score
7.3
out of 10

Quincy is county seat of Adams County, Illinois, United States.

Density
988/km²
people per km²
Founded
1819

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 82°F in the first days to 73°F by the end.

A typical September day in Quincy reaches about 78°F in the afternoon and slips back to 58°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 67°F and 88°F. Set against its neighbours, September runs about 7°F cooler than August and about 13°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18364
28264
38263
48263
58262
68162
78162
88061
98061
108060
117960
127959
137959
147859
157858
167758
177757
187757
197657
207656
217656
227555
237555
247555
257454
267454
277453
287353
297353
307352

How September really feels in Quincy

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.

Quincy 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
Jan36° / 20°1.97.24.29.50.0
Feb40° / 24°2.273.210.40.2
Mar52° / 34°2.99.61.811.72.8
Apr64° / 45°4.411.30.3135.4
May74° / 55°4.612.7014.26.3
Jun83° / 65°4.010.5014.85.8
Jul86° / 69°3.49014.55.2
Aug84° / 66°3.28.4013.65.7
Sep78° / 58°3.37.4012.37.3
Oct65° / 46°2.88.50.210.96.2
Nov51° / 35°2.97.60.99.82.8
Dec40° / 25°2.16.92.89.20.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 49% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 12% of September, with mostly cloudy or overcast conditions the remaining 39%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16436
26436
36436
46535
56535
66535
76535
86436
96337
106337
116238
126139
136040
145941
155941
165842
175842
185842
195842
205842
215941
225941
235941
246040
256040
266040
276139
286238
296238
306238

Chance of precipitation in September

Any precipitation

Quincy gets around 3.3 in of rain over 7.4 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 25% and peaks near 26% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
125
225
325
425
525
625
725
825
925
1025
1125
1225
1326
1426
1526
1626
1726
1826
1926
2025
2125
2225
2324
2424
2524
2624
2724
2824
2924
3024

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 41% of days. Sticky, muggy-or-worse air turns up on roughly 21% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
11420233014
21521222912
31722222811
41922222610
5212322259
6232322248
7252421238
8272420227
9292420216
10312419205
11332419195
12352318194
13372318184
14392317183
15412316173
16432216163
17452215162
18472214152
19482214152
20512113141
21522113131
22542112121
23552012121
24562012111
25581912101
2661191190
2763181180
2863181180
2965171170
3067171060

Wind in September

Winds average 7 mph in September.

Across September, daily wind ranges from about 6 mph on the calmest days to 7 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277calm
287calm
297calm
307calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 54 min 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 78 minutes over September. Sunrise moves from 5:38 AM to 6:06 AM, and sunset from 6:33 PM to 5:44 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:386:33
212.95:396:31
312.85:406:30
412.85:416:28
512.75:426:26
612.75:426:25
712.75:436:23
812.65:446:21
912.65:456:20
1012.55:466:18
1112.55:476:16
1212.45:486:15
1312.45:496:13
1412.35:506:11
1512.35:516:09
1612.35:526:08
1712.25:536:06
1812.25:546:04
1912.15:556:03
2012.15:566:01
2112.05:575:59
2212.05:585:57
2311.95:595:56
2411.96:005:54
2511.96:015:52
2611.86:025:51
2711.86:035:49
2811.76:045:47
2911.76:055:46
3011.66:065:44

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.77 kWh/m².

For context, solar energy here swings from a low near 1.84 kWh/m² to a high of 6.44 kWh/m² in June across the year — September's 4.77 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.3Bright
25.3Bright
35.2Bright
45.2Bright
55.2Bright
65.1Bright
75.1Bright
85.0Bright
95.0Bright
105.0Bright
114.9Bright
124.9Bright
134.8Bright
144.8Bright
154.7Bright
164.7Bright
174.7Bright
184.6Bright
194.6Bright
204.5Bright
214.5Bright
224.5Bright
234.4Bright
244.4Bright
254.3Bright
264.3Bright
274.3Bright
284.2Bright
294.2Bright
304.1Bright
Planning a trip in September

Hazard calendar for Quincy

In seasonPeak

In September, Quincy sits inside its atlantic hurricane season. The full year is below, with each hazard's peak months called out.

Quincy sits in the Atlantic hurricane belt; the season peaks August–October.

Atlantic hurricane
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Quincy?

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

7.3
Sightseeing
1st-best month of the year
6.6
Beach & pool
4th-best month of the year

September is one of the better times to visit Quincy for general sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Quincy in September

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

In September, Quincy sees daytime highs around 78°F and nights near 58°F. Worth packing: light clothes and sun protection. About 7 days see rain.

light clothessun protection

UV index in Quincy 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 Quincy peaks around June 20 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJun 20UV 9Dec 22UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun10Very high
Jul9Very high
Aug8Very high
Sep7High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Quincy 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 Quincy is worst in July — around 16 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (October, 7 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodGoodModerateGoodJul 1716 µg/m³Oct 237 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb12Moderate
Mar12Good
Apr10Good
May13Moderate
Jun14Moderate
Jul16Moderate
Aug14Moderate
Sep11Good
Oct7Good
Nov7Good
Dec8Good
Location & terrain

Where is Quincy?

Quincy sits at 39.9°N, 91.4°W, 568 ft above sea level, in United States. The nearest listed city is Hannibal, 16 mi away.

Topography around Quincy

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

Within 2 miles, the terrain around Quincy has only modest variations in elevation — a maximum elevation change of 230 ft around an average of 551 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 328 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 702 ft.

The land around Quincy is covered by trees (35%) and artificial surfaces (29%) within 2 miles, cropland (53%) and trees (26%) within 10 miles, and cropland (53%) and trees (32%) within 50 miles.

2 miles
230 ft
10 miles
328 ft
50 miles
702 ft
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Hannibal 16 mi · Macomb 53 mi · Burlington 62 mi · Jacksonville 64 mi · Kirksville 65 mi · Wentzville 83 mi · Columbia 84 mi · O'Fallon 86 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 Quincy (39.9356°, -91.4099°, elevation 568 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). 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).