Belleville weather in August

In August, Belleville sees average daytime highs of 86°F and overnight lows near 68°F, with 2.9 in of rain across 9.1 wet days and about 13.5 hours of daylight. It is the 2nd-warmest and 10th-wettest month of the year here.

Day-to-day highs hold fairly steady near 86°F through the month. The sky is clear or mostly clear about 43% of the time in August, and the air most often feels muggy.

Daylight stretches from about 14 hours at the start of August to 12 h 54 min by month's end. Set against the rest of the year, August is Belleville's 3rd-clearest and 12th-windiest month. For the whole year in context, see Belleville's year-round climate.

Daytime high
86°
2nd warmest
Overnight low
68°
11th coldest
Rainfall
2.9 in
9.1 wet days
Daylight
13 h 30 min
5:19 AM – 6:49 PM
Cloud cover
50%
3rd clearest
Wind
5 mph
12th windiest
Solar energy
5.82 kWh/m²
Travel score
5.1
out of 10

Belleville is city in and seat of St. Clair County, Illinois, United States.

Density
691/km²
people per km²
Founded
1814

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in August

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 86°F through the month.

A typical August day in Belleville reaches about 86°F in the afternoon and slips back to 68°F overnight — a 18°F spread between the day's warmth and the night's chill. On most days the high lands between 79°F and 94°F. Set against its neighbours, August runs about 1°F cooler than July and about 6°F warmer than September.

60°80°100°151015202531
Avg high (°F)Avg low (°F)
18770
28770
38770
48769
58769
68769
78769
88769
98769
108769
118769
128769
138769
148768
158668
168668
178668
188668
198668
208668
218668
228668
238668
248668
258667
268667
278667
288667
298567
308567
318566

How August really feels in Belleville

Once humidity and wind are folded in, August averages 2 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
2
heat index over the day's high
Days feeling ≤ 32°F
0
wind chill below the day's low

The story in August is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

Belleville weather by month

How August compares with the rest of the year at a glance. August is the 2nd-warmest and 10th-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 August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 43% of the time in August.

Beyond those clear spells, partly cloudy skies cover about 19% of August, with mostly cloudy or overcast conditions the remaining 39%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15743
25842
35842
45842
55842
65941
75941
85941
96040
106040
116040
126139
136139
146238
156238
166238
176238
186337
196337
206337
216337
226238
236337
246337
256337
266337
276436
286436
296436
306436
316436

Chance of precipitation in August

Any precipitation

Belleville gets around 2.9 in of rain over 9.1 wet days in August. 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 30% on the wettest days.

0%10%20%30%40%151015202531
Rain chance (%)
130
230
330
430
529
629
729
829
930
1030
1130
1230
1330
1430
1530
1630
1730
1830
1930
2029
2129
2229
2329
2429
2529
2629
2728
2828
2928
3027
3127

Humidity in August

DryComfortableHumidMuggyOppressiveMiserable

Most of August feels muggy — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, August lands in the muggy band about 32% of days. Sticky, muggy-or-worse air turns up on roughly 58% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
13132130311
23132131301
34132132291
44132133291
54132133281
64132134271
75132034271
85132034271
95142034261
105141934261
116151934261
126151934251
136161933251
146161933251
156171933251
166171932241
176172032241
186172032241
196172032251
206172032251
216172131251
226162132250
236162132250
246162232250
256162232240
266152232240
277152331230
287152331230
298162331220
309162331210
3110162331200

Wind in August

Winds average 5 mph in August, the calmest month.

Across August, daily wind ranges from about 5 mph on the calmest days to 6 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
266calm
276calm
286calm
296calm
306calm
316calm

Sunrise & sunset in August

DaylightNight

Daylight runs from about 14 hours at the start of August to 12 h 54 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 66 minutes over August. Sunrise moves from 5:05 AM to 5:32 AM, and sunset from 7:07 PM to 6:28 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.05:057:07
214.05:067:06
314.05:077:05
413.95:087:04
513.95:097:03
613.95:107:02
713.85:117:00
813.85:116:59
913.85:126:58
1013.75:136:57
1113.75:146:56
1213.75:156:54
1313.65:166:53
1413.65:176:52
1513.55:186:51
1613.55:196:49
1713.55:206:48
1813.45:216:47
1913.45:216:45
2013.45:226:44
2113.35:236:42
2213.35:246:41
2313.25:256:40
2413.25:266:38
2513.25:276:37
2613.15:286:35
2713.15:296:34
2813.05:306:32
2913.05:316:31
3013.05:316:29
3112.95:326:28

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 5.82 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 — August's 5.82 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
16.2Intense
26.2Intense
36.1Intense
46.1Intense
56.1Intense
66.1Intense
76.0Intense
86.0Intense
96.0Bright
106.0Bright
115.9Bright
125.9Bright
135.9Bright
145.8Bright
155.8Bright
165.8Bright
175.8Bright
185.7Bright
195.7Bright
205.7Bright
215.7Bright
225.6Bright
235.6Bright
245.6Bright
255.5Bright
265.5Bright
275.5Bright
285.4Bright
295.4Bright
305.4Bright
315.3Bright
Planning a trip in August

Is August a good time to visit Belleville?

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

5.1
Sightseeing
6th-best month of the year
7.1
Beach & pool
1st-best month of the year

August is a reasonable time to visit Belleville for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Belleville in August

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

In August, Belleville sees daytime highs around 86°F and nights near 68°F. Pack light clothes. Worth having: rain gear and sun protection. About 9 days see rain.

light clothesrain gearsun protection

UV index in Belleville in August

LowModerateHighVery highExtreme

Clear-sky midday UV in August peaks around 8 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Belleville 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 Belleville in August

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where August falls, not just the annual average.

Air quality in Belleville 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 Belleville?

Belleville sits at 38.5°N, 90.0°W, 515 ft above sea level, in United States. The nearest listed city is Fairview Heights, 5.0 mi away.

Topography around Belleville

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

Within 2 miles, the terrain around Belleville has only modest variations in elevation — a maximum elevation change of 128 ft around an average of 528 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 364 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 981 ft.

The land around Belleville is covered by trees (54%) and artificial surfaces (28%) within 2 miles, trees (39%) and cropland (38%) within 10 miles, and cropland (44%) and trees (42%) within 50 miles.

2 miles
128 ft
10 miles
364 ft
50 miles
981 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
August weather nearby: Fairview Heights 5.0 mi · O'Fallon 6.2 mi · Collinsville 11 mi · East Saint Louis 12 mi · St. Louis 14 mi · Granite City 16 mi · Lemay 16 mi · Oakville 17 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 Belleville (38.52°, -89.984°, elevation 515 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).