Upper Alton weather in September

In September, Upper Alton sees average daytime highs of 79°F and overnight lows near 59°F, with 3.3 in of rain across 7.5 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 83°F in the first days to 75°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 Upper Alton's 1st-clearest and 10th-windiest month. For the whole year in context, see Upper Alton's year-round climate.

Daytime high
79°
4th warmest
Overnight low
59°
9th coldest
Rainfall
3.3 in
7.5 wet days
Daylight
12 h 12 min
5:47 AM – 6:02 PM
Cloud cover
45%
1st clearest
Wind
6 mph
10th windiest
Solar energy
4.75 kWh/m²
Travel score
7.2
out of 10

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 83°F in the first days to 75°F by the end.

A typical September day in Upper Alton reaches about 79°F in the afternoon and slips back to 59°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 69°F and 89°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)
18465
28365
38364
48364
58264
68263
78263
88262
98162
108162
118061
128061
138060
147960
157960
167959
177859
187858
197858
207758
217757
227657
237656
247656
257655
267555
277555
287454
297454
307454

How September really feels in Upper Alton

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.

Upper Alton 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
Jan38° / 24°2.68.23.29.60.0
Feb43° / 27°2.47.6310.50.6
Mar54° / 36°3.610.41.511.73.3
Apr66° / 47°4.611.60.2135.7
May75° / 58°5.013.5014.16.2
Jun83° / 67°4.010.9014.75.6
Jul87° / 70°3.29.5014.45.0
Aug85° / 67°2.98.9013.55.5
Sep79° / 59°3.37.5012.37.2
Oct67° / 48°3.38.40.1116.5
Nov53° / 37°3.68.60.79.93.2
Dec42° / 28°2.48.12.39.30.4

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 14% of September, with mostly cloudy or overcast conditions the remaining 37%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16436
26436
36436
46535
56535
66535
76535
86436
96436
106337
116337
126238
136238
146139
156139
166139
176040
186040
196040
206040
216238
226238
236337
246337
256436
266535
276535
286535
296535
306535

Chance of precipitation in September

Any precipitation

Upper Alton gets around 3.3 in of rain over 7.5 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 25% and peaks near 27% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
125
225
325
425
525
625
725
825
925
1025
1125
1226
1326
1426
1527
1627
1727
1827
1927
2027
2126
2226
2326
2425
2525
2625
2724
2824
2923
3023

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 37% of days. Sticky, muggy-or-worse air turns up on roughly 24% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
11217223118
21318223017
31519222915
41619232814
51820232613
61921232512
72121232411
82322232310
9242223219
10262223218
11282223207
12302223196
13322222186
14332222185
15352121175
16372121174
17392120163
18412020163
19432019153
20462018152
21481917142
22501916141
23531815131
24531815131
25561714121
26571713121
27581713111
28621612100
29621612100
3064151290

Wind in September

Winds average 6 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
96calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
176calm
186calm
196calm
206calm
216calm
226calm
236calm
246calm
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 5:34 AM to 6:01 AM, and sunset from 6:27 PM to 5:39 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:346:27
212.85:356:25
312.85:356:24
412.85:366:22
512.75:376:21
612.75:386:19
712.65:396:17
812.65:406:16
912.65:416:14
1012.55:426:12
1112.55:436:11
1212.45:446:09
1312.45:456:07
1412.35:466:06
1512.35:476:04
1612.25:476:02
1712.25:486:01
1812.25:495:59
1912.15:505:57
2012.15:515:56
2112.05:525:54
2212.05:535:52
2311.95:545:51
2411.95:555:49
2511.95:565:47
2611.85:575:46
2711.85:585:44
2811.75:595:42
2911.76:005:41
3011.66:015:39

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.75 kWh/m².

For context, solar energy here swings from a low near 1.88 kWh/m² to a high of 6.44 kWh/m² in June across the year — September's 4.75 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.3Bright
25.2Bright
35.2Bright
45.2Bright
55.1Bright
65.1Bright
75.0Bright
85.0Bright
95.0Bright
104.9Bright
114.9Bright
124.8Bright
134.8Bright
144.8Bright
154.7Bright
164.7Bright
174.7Bright
184.6Bright
194.6Bright
204.5Bright
214.5Bright
224.5Bright
234.5Bright
244.4Bright
254.4Bright
264.4Bright
274.3Bright
284.3Bright
294.3Bright
304.2Bright
Planning a trip in September

Is September a good time to visit Upper Alton?

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
6.8
Beach & pool
3rd-best month of the year

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

What to pack for Upper Alton in September

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

In September, Upper Alton sees daytime highs around 79°F and nights near 59°F. Worth packing: light clothes and sun protection. About 8 days see rain.

light clothessun protection

UV index in Upper Alton 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 Upper Alton peaks around June 21 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highModerateJun 21UV 9Dec 23UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr7High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep7High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Upper Alton 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 Upper Alton is worst in August — around 18 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (October, 8 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodModerateGoodAug 1018 µg/m³Oct 228 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb13Moderate
Mar13Moderate
Apr11Good
May14Moderate
Jun16Moderate
Jul18Moderate
Aug18Moderate
Sep13Moderate
Oct8Good
Nov9Good
Dec10Good
Location & terrain

Where is Upper Alton?

Upper Alton sits at 38.9°N, 90.2°W, 545 ft above sea level, in United States. The nearest listed city is Alton, 2.5 mi away.

Topography around Upper Alton

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

Within 2 miles, the terrain around Upper Alton has only modest variations in elevation — a maximum elevation change of 249 ft around an average of 518 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 620 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 751 ft.

The land around Upper Alton is covered by trees (55%) and artificial surfaces (22%) within 2 miles, trees (41%) and cropland (32%) within 10 miles, and cropland (49%) and trees (37%) within 50 miles.

2 miles
249 ft
10 miles
620 ft
50 miles
751 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Alton 2.5 mi · Godfrey 3.7 mi · Old Jamestown 8.7 mi · Spanish Lake 9.3 mi · Florissant 12 mi · Edwardsville 12 mi · Ferguson 14 mi · Granite City 14 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 Upper Alton (38.9114°, -90.1507°, elevation 545 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).