Janesville weather in August

In August, Janesville sees average daytime highs of 79°F and overnight lows near 62°F, with 3.6 in of rain across 10.3 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 79°F through the month. The sky is clear or mostly clear about 35% of the time in August, and the air most often feels comfortable.

Daylight stretches from about 14 h 24 min at the start of August to 13 h 06 min by month's end. Set against the rest of the year, August is Janesville's 2nd-clearest and 12th-windiest month. For the whole year in context, see Janesville's year-round climate.

Daytime high
79°
2nd warmest
Overnight low
62°
11th coldest
Rainfall
3.6 in
10.3 wet days
Daylight
13 h 48 min
5:08 AM – 6:53 PM
Cloud cover
55%
2nd clearest
Wind
6 mph
12th windiest
Solar energy
5.37 kWh/m²
Travel score
6.7
out of 10

Janesville is city in and county seat of Rock County, Wisconsin, United States.

Density
720/km²
people per km²
Founded
1853

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 79°F through the month.

A typical August day in Janesville reaches about 79°F in the afternoon and slips back to 62°F overnight — a 17°F spread between the day's warmth and the night's chill. On most days the high lands between 72°F and 87°F. Set against its neighbours, August runs about 2°F cooler than July and about 7°F warmer than September.

50°60°70°80°90°151015202531
Avg high (°F)Avg low (°F)
18164
28163
38163
48063
58063
68063
78063
88063
98063
108062
118062
128062
137962
147962
157962
167962
177962
187962
197962
207962
217962
227961
237961
247961
257961
267961
277861
287860
297860
307860
317860

How August really feels in Janesville

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.

Janesville 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
Jan28° / 14°1.87.76.49.20.0
Feb32° / 17°1.76.95.510.30.0
Mar44° / 28°2.49.43.511.61.0
Apr57° / 39°4.0121.613.13.7
May68° / 50°3.912.20.114.45.9
Jun78° / 60°4.111.6015.16.4
Jul81° / 64°3.310.1014.86.5
Aug79° / 62°3.610.3013.76.7
Sep72° / 54°3.38.8012.36.9
Oct59° / 42°2.88.90.310.84.8
Nov45° / 31°2.2829.61.1
Dec33° / 20°2.07.858.90.0

Cloud cover in August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 35% 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 46%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15644
25644
35644
45644
55545
65545
75446
85347
95347
105149
115149
125149
135149
145149
155149
165248
175248
185248
195248
205347
215347
225347
235446
245545
255545
265743
275743
285842
295842
305941
315941

Chance of precipitation in August

Any precipitation

Janesville gets around 3.6 in of rain over 10.3 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 33% and peaks near 35% on the wettest days.

0%10%20%30%40%50%151015202531
Rain chance (%)
133
233
332
432
532
632
732
832
932
1033
1133
1233
1333
1434
1534
1634
1734
1834
1935
2035
2135
2235
2334
2434
2533
2633
2732
2831
2931
3030
3130

Humidity in August

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, August lands in the comfortable band about 26% of days. Sticky, muggy-or-worse air turns up on roughly 30% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
115262622101
215262622101
315262622100
416262622100
516262622100
61627262290
71726252290
81726252290
91826252290
101826252280
111826252280
121927242280
131927242280
141927242280
151927242270
161927242370
171926242370
182026242370
192026242470
202026242460
212026242460
222026242460
232026242460
242126242460
252226242360
262325232360
272425232260
282525232250
292625232150
302825222050
312925221950

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 7 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
307calm
317calm

Sunrise & sunset in August

DaylightNight

Daylight runs from about 14 h 24 min at the start of August to 13 h 06 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 78 minutes over August. Sunrise moves from 4:51 AM to 5:24 AM, and sunset from 7:13 PM to 6:28 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.44:517:13
214.34:527:12
314.34:537:11
414.24:557:09
514.24:567:08
614.24:577:07
714.14:587:05
814.14:597:04
914.05:007:03
1014.05:017:01
1114.05:027:00
1213.95:036:59
1313.95:046:57
1413.85:056:56
1513.85:066:54
1613.85:086:53
1713.75:096:51
1813.75:106:50
1913.65:116:48
2013.65:126:47
2113.55:136:45
2213.55:146:43
2313.45:156:42
2413.45:166:40
2513.35:186:38
2613.35:196:37
2713.35:206:35
2813.25:216:33
2913.25:226:32
3013.15:236:30
3113.15:246:28

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 5.37 kWh/m².

For context, solar energy here swings from a low near 1.59 kWh/m² to a high of 6.29 kWh/m² in June across the year — August's 5.37 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
15.9Bright
25.8Bright
35.8Bright
45.8Bright
55.7Bright
65.7Bright
75.7Bright
85.6Bright
95.6Bright
105.5Bright
115.5Bright
125.5Bright
135.4Bright
145.4Bright
155.4Bright
165.3Bright
175.3Bright
185.3Bright
195.3Bright
205.2Bright
215.2Bright
225.2Bright
235.2Bright
245.1Bright
255.1Bright
265.1Bright
275.1Bright
285.0Bright
295.0Bright
305.0Bright
315.0Bright
Planning a trip in August

Is August a good time to visit Janesville?

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

6.7
Sightseeing
2nd-best month of the year
6.5
Beach & pool
2nd-best month of the year

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

What to pack for Janesville in August

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

In August, Janesville sees daytime highs around 79°F and nights near 62°F. Worth packing: light clothes, rain gear and sun protection. About 10 days see rain.

light clothesrain gearsun protection

UV index in Janesville 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 Janesville peaks around June 19 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 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 19UV 9Dec 22UV 1
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar4Moderate
Apr6High
May8Very high
Jun9Very high
Jul8Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low

Air quality in Janesville 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 Janesville is worst in July — around 15 µg/m³ PM2.5 (moderate), about 2.0× the cleanest month (October, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateModerateGoodJul 1715 µg/m³Oct 238 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb13Moderate
Mar13Moderate
Apr12Good
May13Moderate
Jun14Moderate
Jul15Moderate
Aug14Moderate
Sep11Good
Oct8Good
Nov8Good
Dec9Good
Location & terrain

Where is Janesville?

Janesville sits at 42.7°N, 89.0°W, 837 ft above sea level, in United States. The nearest listed city is Beloit, 12 mi away.

Topography around Janesville

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

Within 2 miles, the terrain around Janesville has only modest variations in elevation — a maximum elevation change of 200 ft around an average of 833 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 348 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,063 ft.

The land around Janesville is covered by artificial surfaces (37%), trees (34%) and grassland (22%) within 2 miles, cropland (58%) within 10 miles, and cropland (56%) and trees (22%) within 50 miles.

2 miles
200 ft
10 miles
348 ft
50 miles
1,063 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
August weather nearby: Beloit 12 mi · Machesney Park 23 mi · Loves Park 25 mi · Rockford 29 mi · Fitchburg 30 mi · Belvidere 30 mi · Madison 33 mi · Sun Prairie 36 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 Janesville (42.6828°, -89.0187°, elevation 837 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).