Fairview Heights weather in September

In September, Fairview Heights sees average daytime highs of 80°F and overnight lows near 60°F, with 3.2 in of rain across 7.6 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 8th-wettest month of the year here.

Highs ease over the month, from about 84°F in the first days to 76°F by the end. The sky is clear or mostly clear about 48% 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 Fairview Heights's 1st-clearest and 10th-windiest month. For the whole year in context, see Fairview Heights's year-round climate.

Daytime high
80°
4th warmest
Overnight low
60°
9th coldest
Rainfall
3.2 in
7.6 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
4.76 kWh/m²
Travel score
7.0
out of 10

Fairview Heights is city in St. Clair County, Illinois, United States.

Density
561/km²
people per km²

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 84°F in the first days to 76°F by the end.

A typical September day in Fairview Heights reaches about 80°F in the afternoon and slips back to 60°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 70°F and 90°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)
18566
28566
38465
48465
58465
68364
78364
88363
98263
108262
118262
128162
138161
148061
158060
168060
177960
187959
197959
207858
217858
227858
237757
247757
257756
267656
277656
287655
297655
307554

How September really feels in Fairview Heights

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.

Fairview Heights weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan40° / 25°2.98.32.99.60.0
Feb45° / 29°2.67.62.610.51.0
Mar56° / 38°3.810.81.311.73.7
Apr67° / 48°4.811.50.1135.9
May76° / 58°5.113.3014.16.3
Jun85° / 67°4.110.8014.65.2
Jul88° / 71°3.49.8014.44.6
Aug86° / 68°2.99.1013.55.1
Sep80° / 60°3.27.6012.37.0
Oct68° / 49°3.58.40116.7
Nov55° / 38°3.78.70.69.93.6
Dec44° / 29°2.88.529.40.7

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 48% 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 37%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16535
26535
36535
46535
56535
66535
76535
86535
96535
106436
116337
126238
136238
146238
156040
166040
176040
186040
196040
206040
216040
226139
236139
246238
256337
266337
276436
286436
296436
306535

Chance of precipitation in September

Any precipitation

Fairview Heights gets around 3.2 in of rain over 7.6 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 (%)
127
227
327
427
526
626
725
825
925
1025
1125
1225
1325
1425
1526
1626
1726
1826
1926
2026
2126
2226
2326
2425
2525
2624
2724
2823
2922
3022

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 35% of days. Sticky, muggy-or-worse air turns up on roughly 25% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
11117233018
21217233017
31418232916
41519232814
51620232813
61820232712
72021232610
8212223259
9232223248
10252322237
11262322226
12282322215
13302322215
14322321204
15332221194
16352220193
17372220183
18392219182
19412119172
20432118162
21452017161
22482017151
23501916141
24511915141
25531815131
26551814121
27561714121
28591713110
29601613110
30621612100

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
256calm
266calm
276calm
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 5:33 AM to 6:00 AM, and sunset from 6:26 PM to 5:39 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:336:26
212.85:346:24
312.85:356:23
412.85:366:21
512.75:376:20
612.75:386:18
712.65:396:16
812.65:406:15
912.55:416:13
1012.55:416:12
1112.55:426:10
1212.45:436:08
1312.45:446:07
1412.35:456:05
1512.35:466:03
1612.25:476:02
1712.25:486:00
1812.25:495:58
1912.15:505:57
2012.15:515:55
2112.05:515:53
2212.05:525:52
2311.95:535:50
2411.95:545:48
2511.95:555:47
2611.85:565:45
2711.85:575:44
2811.75:585:42
2911.75:595:40
3011.66:005:39

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.76 kWh/m².

For context, solar energy here swings from a low near 1.91 kWh/m² to a high of 6.47 kWh/m² in June across the year — September's 4.76 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.3Bright
25.3Bright
35.2Bright
45.2Bright
55.1Bright
65.1Bright
75.1Bright
85.0Bright
95.0Bright
104.9Bright
114.9Bright
124.8Bright
134.8Bright
144.8Bright
154.7Bright
164.7Bright
174.7Bright
184.6Bright
194.6Bright
204.6Bright
214.5Bright
224.5Bright
234.5Bright
244.5Bright
254.4Bright
264.4Bright
274.4Bright
284.3Bright
294.3Bright
304.3Bright
Planning a trip in September

Is September a good time to visit Fairview Heights?

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

7.0
Sightseeing
1st-best month of the year
7.0
Beach & pool
2nd-best month of the year

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

What to pack for Fairview Heights in September

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

In September, Fairview Heights sees daytime highs around 80°F and nights near 60°F. Worth packing: light clothes and sun protection. About 8 days see rain.

light clothessun protection

UV index in Fairview Heights 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 Fairview Heights peaks around June 22 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (moderate).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJun 22UV 9Dec 23UV 2
UV index (midday)Level
Jan2Moderate
Feb3Moderate
Mar5High
Apr7High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep7High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Fairview Heights 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 Fairview Heights is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (October, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1418 µg/m³Oct 238 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb12Good
Mar12Good
Apr11Good
May14Moderate
Jun16Moderate
Jul18Moderate
Aug15Moderate
Sep12Moderate
Oct8Good
Nov8Good
Dec9Good
Location & terrain

Where is Fairview Heights?

Fairview Heights sits at 38.6°N, 90.0°W, 584 ft above sea level, in United States. The nearest listed city is O'Fallon, 4.3 mi away.

Topography around Fairview Heights

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

Within 2 miles, the terrain around Fairview Heights has only modest variations in elevation — a maximum elevation change of 141 ft around an average of 577 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 358 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 974 ft.

The land around Fairview Heights is covered by trees (46%) and artificial surfaces (22%) within 2 miles, trees (40%) and cropland (31%) within 10 miles, and cropland (46%) and trees (41%) within 50 miles.

2 miles
141 ft
10 miles
358 ft
50 miles
974 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: O'Fallon 4.3 mi · Belleville 5.0 mi · Collinsville 5.6 mi · East Saint Louis 8.7 mi · St. Louis 12 mi · Granite City 12 mi · Edwardsville 16 mi · Lemay 16 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 Fairview Heights (38.5889°, -89.9904°, elevation 584 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).