Jacksonville weather in August

In August, Jacksonville sees average daytime highs of 84°F and overnight lows near 66°F, with 3.0 in of rain across 9 wet days and about 13.6 hours of daylight. It is the 2nd-warmest and 7th-wettest month of the year here.

Day-to-day highs hold fairly steady near 84°F through the month. The sky is clear or mostly clear about 42% of the time in August, and the air most often feels muggy.

Daylight stretches from about 14 h 06 min at the start of August to 13 hours by month's end. Set against the rest of the year, August is Jacksonville's 2nd-clearest and 12th-windiest month. For the whole year in context, see Jacksonville's year-round climate.

Daytime high
84°
2nd warmest
Overnight low
66°
11th coldest
Rainfall
3.0 in
9 wet days
Daylight
13 h 36 min
5:18 AM – 6:52 PM
Cloud cover
49%
2nd clearest
Wind
6 mph
12th windiest
Solar energy
5.74 kWh/m²
Travel score
5.7
out of 10

Jacksonville is city in Morgan County, Illinois, United States.

Density
691/km²
people per km²
Founded
1825

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 84°F through the month.

A typical August day in Jacksonville reaches about 84°F in the afternoon and slips back to 66°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 77°F and 92°F. Set against its neighbours, August runs on par with July and about 6°F warmer than September.

50°60°70°80°90°151015202531
Avg high (°F)Avg low (°F)
18567
28567
38567
48567
58567
68567
78567
88566
98566
108466
118466
128466
138466
148466
158466
168466
178466
188466
198465
208465
218465
228465
238465
248465
258465
268465
278465
288464
298364
308364
318364

How August really feels in Jacksonville

Once humidity and wind are folded in, August 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

August sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Jacksonville weather by month

How August compares with the rest of the year at a glance. August is the 2nd-warmest and 7th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan36° / 21°2.37.749.50.0
Feb41° / 24°2.27.23.410.40.3
Mar52° / 34°3.110.31.611.72.8
Apr64° / 45°4.611.50.4135.4
May74° / 55°4.413.4014.26.2
Jun82° / 65°4.111.1014.85.8
Jul85° / 68°3.39.5014.55.3
Aug84° / 66°3.09013.65.7
Sep78° / 58°2.97.5012.37.3
Oct66° / 46°3.08.30.110.96.3
Nov52° / 35°3.28.20.99.82.8
Dec40° / 26°2.37.42.79.20.2

Cloud cover in August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 42% 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 38%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
16139
26238
36238
46139
56139
66139
76139
86139
96139
106139
116139
126139
136139
146139
156238
166238
176139
186139
196238
206238
216139
226139
236139
246139
256139
266238
276238
286238
296337
306337
316337

Chance of precipitation in August

Any precipitation

Jacksonville gets around 3.0 in of rain over 9 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
429
529
629
729
829
929
1030
1130
1230
1330
1430
1530
1630
1729
1829
1930
2030
2130
2229
2329
2429
2528
2628
2727
2827
2926
3026
3126

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 29% of days. Sticky, muggy-or-worse air turns up on roughly 49% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
16152626251
26152627251
36162627241
46162628231
56162628231
66162628221
76172628221
87172629211
97172529211
107182529201
117182429201
128182429201
138192429191
148192429191
158192429191
168192429191
178192429191
188192429191
198192429191
208192430191
218192430190
228192430190
238192430190
249192430190
259192430190
269192429180
2710192429180
2811192429170
2912192429160
3013192428150
3115202428140

Wind in August

Winds average 6 mph in August, the calmest month.

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

0246810151015202531
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
286calm
296calm
306calm
316calm

Sunrise & sunset in August

DaylightNight

Daylight runs from about 14 h 06 min at the start of August to 13 hours by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 66 minutes over August. Sunrise moves from 5:03 AM to 5:32 AM, and sunset from 7:11 PM to 6:30 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.15:037:11
214.15:047:09
314.15:057:08
414.05:067:07
514.05:077:06
613.95:087:05
713.95:097:04
813.95:107:03
913.85:117:01
1013.85:127:00
1113.85:136:59
1213.75:146:58
1313.75:156:56
1413.75:166:55
1513.65:176:54
1613.65:186:52
1713.55:196:51
1813.55:206:50
1913.55:216:48
2013.45:226:47
2113.45:236:45
2213.35:236:44
2313.35:246:42
2413.35:256:41
2513.25:266:39
2613.25:276:38
2713.15:286:36
2813.15:296:35
2913.05:306:33
3013.05:316:31
3113.05:326:30

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 5.74 kWh/m².

For context, solar energy here swings from a low near 1.84 kWh/m² to a high of 6.46 kWh/m² in June across the year — August's 5.74 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
16.2Intense
26.1Intense
36.1Intense
46.1Intense
56.1Intense
66.0Intense
76.0Intense
86.0Bright
96.0Bright
105.9Bright
115.9Bright
125.9Bright
135.8Bright
145.8Bright
155.8Bright
165.7Bright
175.7Bright
185.7Bright
195.6Bright
205.6Bright
215.6Bright
225.5Bright
235.5Bright
245.5Bright
255.5Bright
265.4Bright
275.4Bright
285.4Bright
295.3Bright
305.3Bright
315.3Bright
Planning a trip in August

Is August a good time to visit Jacksonville?

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

5.7
Sightseeing
5th-best month of the year
7.3
Beach & pool
1st-best month of the year

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

What to pack for Jacksonville in August

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

In August, Jacksonville sees daytime highs around 84°F and nights near 66°F. Pack light clothes. Worth having: rain gear and sun protection. About 9 days see rain.

light clothesrain gearsun protection

UV index in Jacksonville 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 Jacksonville peaks around June 21 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 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highModerateJun 21UV 9Dec 22UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep7High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Jacksonville 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 Jacksonville is worst in July — around 16 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (October, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodModerateGoodJul 1716 µg/m³Oct 238 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb13Moderate
Mar12Moderate
Apr11Good
May14Moderate
Jun14Moderate
Jul16Moderate
Aug14Moderate
Sep11Good
Oct8Good
Nov8Good
Dec9Good
Location & terrain

Where is Jacksonville?

Jacksonville sits at 39.7°N, 90.2°W, 610 ft above sea level, in United States. The nearest listed city is Springfield, 32 mi away.

Topography around Jacksonville

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

Within 2 miles, the terrain around Jacksonville has only modest variations in elevation — a maximum elevation change of 177 ft around an average of 604 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 243 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 604 ft.

The land around Jacksonville is covered by trees (32%), grassland (25%) and cropland (23%) within 2 miles, cropland (74%) within 10 miles, and cropland (65%) and trees (27%) within 50 miles.

2 miles
177 ft
10 miles
243 ft
50 miles
604 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
August weather nearby: Springfield 32 mi · Godfrey 54 mi · Macomb 55 mi · Upper Alton 57 mi · Alton 58 mi · Hannibal 60 mi · Old Jamestown 62 mi · Quincy 64 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 Jacksonville (39.7339°, -90.229°, elevation 610 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).