Lake Forest weather in August

In August, Lake Forest sees average daytime highs of 77°F and overnight lows near 70°F, with 3.8 in of rain across 10.7 wet days and about 13.7 hours of daylight. It is the 2nd-warmest and 4th-wettest month of the year here.

Day-to-day highs hold fairly steady near 77°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 h 18 min at the start of August to 13 hours by month's end. Set against the rest of the year, August is Lake Forest's 2nd-clearest and 12th-windiest month. For the whole year in context, see Lake Forest's year-round climate.

Daytime high
77°
2nd warmest
Overnight low
70°
11th coldest
Rainfall
3.8 in
10.7 wet days
Daylight
13 h 42 min
5:04 AM – 6:47 PM
Cloud cover
50%
2nd clearest
Wind
10 mph
12th windiest
Solar energy
5.55 kWh/m²
Travel score
7.0
out of 10

Lake Forest is city in Lake County, Illinois, United States.

Density
435/km²
people per km²
Founded
1861

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 77°F through the month.

A typical August day in Lake Forest reaches about 77°F in the afternoon and slips back to 70°F overnight — a 7°F spread between the day's warmth and the night's chill. On most days the high lands between 70°F and 84°F. Set against its neighbours, August runs on par with July and about 6°F warmer than September.

60°70°80°151015202531
Avg high (°F)Avg low (°F)
17871
27871
37871
47871
57871
67871
77771
87771
97771
107770
117770
127770
137770
147770
157770
167770
177770
187770
197770
207770
217770
227770
237770
247669
257669
267669
277669
287669
297669
307669
317668

How August really feels in Lake Forest

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.

Lake Forest weather by month

How August compares with the rest of the year at a glance. August is the 2nd-warmest and 4th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan30° / 21°2.99.879.30.0
Feb31° / 21°2.47.75.110.30.0
Mar37° / 29°3.09.83.211.60.0
Apr46° / 39°4.8121.413.11.3
May58° / 50°4.111.7014.44.1
Jun71° / 64°3.510.50156.5
Jul78° / 70°3.110.5014.86.8
Aug77° / 70°3.810.7013.77.0
Sep71° / 63°3.39.5012.36.8
Oct58° / 51°4.010.50.110.84.4
Nov46° / 39°3.4101.39.61.2
Dec36° / 28°3.1104.990.0

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 17% of August, with mostly cloudy or overcast conditions the remaining 41%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15941
25941
35941
45941
55941
65941
75842
85842
95842
105842
115941
125842
135842
145941
155941
165941
176040
186040
195941
205941
216040
225941
235941
245941
256040
266040
276040
286139
296139
306238
316238

Chance of precipitation in August

Any precipitation

Lake Forest gets around 3.8 in of rain over 10.7 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 34% and peaks near 36% on the wettest days.

0%10%20%30%40%50%151015202531
Rain chance (%)
133
233
333
433
533
633
733
834
934
1035
1135
1235
1336
1436
1536
1636
1736
1836
1936
2036
2136
2235
2335
2434
2533
2632
2731
2831
2930
3029
3129

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 47% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
16182530192
26182530192
36182630192
46182630192
56182630191
66182630191
76182630191
87182629181
97192629181
107192629181
117192629181
127192729171
137192728171
147192728171
157192829161
167192829161
178182829161
188182929161
198182930160
207172930160
217172930160
227172930160
237172930160
248172930160
258182930160
268182930150
279182830150
2810192829140
2910192829140
3011202729130
3112202728120

Wind in August

Winds average 10 mph in August, the calmest month.

Across August, daily wind ranges from about 10 mph on the calmest days to 11 mph at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (mph)Feels
110light breeze
210light breeze
310light breeze
410light breeze
510light breeze
610light breeze
710light breeze
810light breeze
910light breeze
1010light breeze
1110light breeze
1210light breeze
1310light breeze
1410light breeze
1510light breeze
1610light breeze
1710light breeze
1810light breeze
1910light breeze
2010light breeze
2110light breeze
2210light breeze
2310light breeze
2410light breeze
2510light breeze
2610light breeze
2710light breeze
2811light breeze
2911light breeze
3011light breeze
3111light breeze

Sunrise & sunset in August

DaylightNight

Daylight runs from about 14 h 18 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 78 minutes over August. Sunrise moves from 4:48 AM to 5:20 AM, and sunset from 7:07 PM to 6:23 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.34:487:07
214.34:497:06
314.24:507:05
414.24:517:04
514.24:527:02
614.14:537:01
714.14:547:00
814.14:556:59
914.04:566:57
1014.04:576:56
1113.94:586:54
1213.94:596:53
1313.95:006:52
1413.85:016:50
1513.85:036:49
1613.75:046:47
1713.75:056:46
1813.65:066:44
1913.65:076:43
2013.65:086:41
2113.55:096:40
2213.55:106:38
2313.45:116:36
2413.45:126:35
2513.35:136:33
2613.35:146:31
2713.25:166:30
2813.25:176:28
2913.15:186:26
3013.15:196:25
3113.05:206:23

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 5.55 kWh/m².

For context, solar energy here swings from a low near 1.48 kWh/m² to a high of 6.5 kWh/m² in June across the year — August's 5.55 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
16.1Intense
26.0Intense
36.0Intense
46.0Bright
55.9Bright
65.9Bright
75.8Bright
85.8Bright
95.8Bright
105.7Bright
115.7Bright
125.7Bright
135.6Bright
145.6Bright
155.6Bright
165.5Bright
175.5Bright
185.5Bright
195.4Bright
205.4Bright
215.4Bright
225.4Bright
235.3Bright
245.3Bright
255.3Bright
265.3Bright
275.2Bright
285.2Bright
295.2Bright
305.1Bright
315.1Bright
Planning a trip in August

Is August a good time to visit Lake Forest?

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

7.0
Sightseeing
1st-best month of the year
6.2
Beach & pool
2nd-best month of the year

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

What to pack for Lake Forest in August

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

In August, Lake Forest sees daytime highs around 77°F and nights near 70°F. Worth packing: light clothes, rain gear and sun protection. About 11 days see rain.

light clothesrain gearsun protection

Sea temperature near Lake Forest in August

The nearest coast averages about 71°F in August — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 8 mi away) is warmest in August at about 71°F and coldest in March near 36°F.

It's comfortable for a long swim from Jul 18 to Sep 8 — about 1.7 months when the water holds above 68°F.

30°40°50°60°70°80°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°F)Comfort
Jan38Bracing
Feb36Bracing
Mar36Bracing
Apr38Bracing
May43Bracing
Jun55Bracing
Jul68Refreshing
Aug71Refreshing
Sep67Cool
Oct57Bracing
Nov47Bracing
Dec42Bracing

UV index in Lake Forest in August

LowModerateHighVery highExtreme

Clear-sky midday UV in August peaks around 8 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Lake Forest peaks around June 22 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJun 22UV 9Jan 1UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar4Moderate
Apr6High
May7Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low

Air quality in Lake Forest 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 Lake Forest is worst in July — around 21 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (October, 10 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodJul 921 µg/m³Oct 2410 µg/m³
PM2.5 (µg/m³)Level
Jan12Moderate
Feb15Moderate
Mar18Moderate
Apr19Moderate
May20Moderate
Jun21Moderate
Jul21Moderate
Aug18Moderate
Sep15Moderate
Oct10Good
Nov10Good
Dec11Good
Location & terrain

Where is Lake Forest?

Lake Forest sits at 42.3°N, 87.8°W, 689 ft above sea level, in United States. The nearest listed city is North Chicago, 4.3 mi away.

Topography around Lake Forest

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

Within 2 miles, the terrain around Lake Forest has only modest variations in elevation — a maximum elevation change of 200 ft around an average of 666 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 318 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 892 ft.

The land around Lake Forest is covered by trees (54%) and water (23%) within 2 miles, water (39%) and trees (29%) within 10 miles, and water (43%) within 50 miles.

2 miles
200 ft
10 miles
318 ft
50 miles
892 ft
treesgrasslandcroplandartificial surfaceswater
August weather nearby: North Chicago 4.3 mi · Highland Park 5.6 mi · Libertyville 6.2 mi · Deerfield 6.2 mi · Waukegan 7.5 mi · Vernon Hills 7.5 mi · Gurnee 8.1 mi · Mundelein 8.1 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 Lake Forest (42.2586°, -87.8406°, elevation 689 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. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. 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).