Waukesha weather in September

In September, Waukesha sees average daytime highs of 72°F and overnight lows near 54°F, with 3.0 in of rain across 8.7 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 6th-wettest month of the year here.

Highs ease over the month, from about 76°F in the first days to 67°F by the end. The sky is clear or mostly clear about 39% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Waukesha's 1st-clearest and 9th-windiest month. For the whole year in context, see Waukesha's year-round climate.

Daytime high
72°
4th warmest
Overnight low
54°
9th coldest
Rainfall
3.0 in
8.7 wet days
Daylight
12 h 18 min
5:39 AM – 5:56 PM
Cloud cover
52%
1st clearest
Wind
7 mph
9th windiest
Solar energy
4.29 kWh/m²
Travel score
6.9
out of 10

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

Density
1,109/km²
people per km²
Founded
1839

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 76°F in the first days to 67°F by the end.

A typical September day in Waukesha reaches about 72°F in the afternoon and slips back to 54°F overnight — a 18°F spread between the day's warmth and the night's chill. On most days the high lands between 61°F and 82°F. Set against its neighbours, September runs about 7°F cooler than August and about 13°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
17760
27759
37659
47659
57658
67658
77558
87557
97457
107456
117456
127356
137355
147355
157255
167254
177254
187153
197153
207053
217052
226952
236951
246951
256851
266850
276750
286749
296749
306649

How September really feels in Waukesha

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.

Waukesha weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 6th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan28° / 15°1.88.36.89.20.0
Feb32° / 18°1.775.610.20.0
Mar43° / 28°2.39.34.111.60.8
Apr55° / 38°4.012.11.713.13.4
May67° / 49°3.811.7014.45.8
Jun77° / 59°3.811.2015.16.5
Jul81° / 64°3.410.1014.86.5
Aug79° / 62°3.610.3013.86.7
Sep72° / 54°3.08.7012.36.9
Oct59° / 43°2.98.90.310.84.7
Nov45° / 32°2.28.11.99.51.1
Dec33° / 21°2.07.85.18.90.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 39% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 16% of September, with mostly cloudy or overcast conditions the remaining 45%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15743
25743
35743
45842
55842
65842
75743
85743
95743
105743
115743
125644
135644
145545
155644
165545
175545
185545
195446
205446
215446
225446
235347
245248
255248
265149
275149
285149
295149
305050

Chance of precipitation in September

Any precipitation

Waukesha gets around 3.0 in of rain over 8.7 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 30% and peaks near 31% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
129
229
328
428
528
628
728
828
928
1028
1129
1229
1330
1430
1531
1631
1731
1831
1931
2031
2131
2231
2331
2431
2531
2630
2730
2830
2929
3029

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 57% of days. Sticky, muggy-or-worse air turns up on roughly 10% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1312423184
2332423173
3352422163
4382322153
5392322142
6412221132
7432221122
8452220121
9462120111
10482119111
11492119101
12512018101
1353201791
1453201791
1556191690
1658191580
1758191580
1861181470
1963171370
2065171260
2167161160
2269151150
2371141050
247314940
257413940
267612840
277811830
287911730
298010730
30829720

Wind in September

Winds average 7 mph in September.

Across September, daily wind ranges from about 7 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (mph)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167light breeze
178light breeze
188light breeze
198light breeze
208light breeze
218light breeze
228light breeze
238light breeze
248light breeze
258light breeze
268light breeze
278light breeze
288light breeze
298light breeze
308light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 hours 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 84 minutes over September. Sunrise moves from 5:22 AM to 5:55 AM, and sunset from 6:24 PM to 5:30 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:226:24
213.05:236:22
312.95:246:20
412.95:256:18
512.85:266:16
612.85:276:14
712.75:286:13
812.75:306:11
912.65:316:09
1012.65:326:07
1112.55:336:05
1212.55:346:03
1312.45:356:02
1412.45:366:00
1512.35:375:58
1612.35:395:56
1712.25:405:54
1812.25:415:52
1912.15:425:50
2012.15:435:48
2112.05:445:47
2212.05:455:45
2311.95:475:43
2411.95:485:41
2511.85:495:39
2611.85:505:37
2711.75:515:35
2811.75:525:34
2911.65:535:32
3011.65:555:30

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.29 kWh/m².

For context, solar energy here swings from a low near 1.55 kWh/m² to a high of 6.36 kWh/m² in June across the year — September's 4.29 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.9Bright
24.8Bright
34.8Bright
44.8Bright
54.7Bright
64.7Bright
74.6Bright
84.6Bright
94.5Bright
104.5Bright
114.4Bright
124.4Bright
134.3Bright
144.3Bright
154.3Bright
164.2Bright
174.2Bright
184.2Bright
194.1Bright
204.1Bright
214.0Bright
224.0Bright
234.0Moderate
243.9Moderate
253.9Moderate
263.8Moderate
273.8Moderate
283.8Moderate
293.7Moderate
303.7Moderate
Planning a trip in September

Is September a good time to visit Waukesha?

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

6.9
Sightseeing
1st-best month of the year
4.8
Beach & pool
4th-best month of the year

September is a reasonable time to visit Waukesha for sightseeing.

What to pack for Waukesha in September

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

In September, Waukesha sees daytime highs around 72°F and nights near 54°F. Worth packing: light clothes and rain gear. About 9 days see rain.

light clothesrain gear

Sea temperature near Waukesha in September

The nearest coast averages about 66°F in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 20 mi away) is warmest in August at about 70°F and coldest in March near 36°F.

It's comfortable for a long swim from Jul 29 to Aug 30 — about 1.1 months when the water holds above 68°F.

30°40°50°60°70°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarm
Sea temperature (°F)Comfort
Jan38Bracing
Feb36Bracing
Mar36Bracing
Apr38Bracing
May42Bracing
Jun54Bracing
Jul67Cool
Aug70Refreshing
Sep66Cool
Oct56Bracing
Nov46Bracing
Dec41Bracing

UV index in Waukesha in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 6 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Waukesha peaks around June 20 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 20UV 9Jan 1UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar4Moderate
Apr6High
May8Very high
Jun9Very high
Jul8Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov2Low
Dec1Low

Air quality in Waukesha 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 Waukesha is worst in July — around 17 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (October, 9 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodJul 1616 µg/m³Oct 239 µg/m³
PM2.5 (µg/m³)Level
Jan12Good
Feb14Moderate
Mar15Moderate
Apr13Moderate
May15Moderate
Jun16Moderate
Jul17Moderate
Aug15Moderate
Sep12Moderate
Oct9Good
Nov9Good
Dec10Good
Location & terrain

Where is Waukesha?

Waukesha sits at 43.0°N, 88.2°W, 814 ft above sea level, in United States. The nearest listed city is New Berlin, 6.8 mi away.

Topography around Waukesha

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

Within 2 miles, the terrain around Waukesha has only modest variations in elevation — a maximum elevation change of 285 ft around an average of 883 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 561 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 846 ft.

The land around Waukesha is covered by artificial surfaces (49%) and trees (33%) within 2 miles, trees (46%) and grassland (28%) within 10 miles, and cropland (34%), water (27%) and trees (21%) within 50 miles.

2 miles
285 ft
10 miles
561 ft
50 miles
846 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: New Berlin 6.8 mi · Brookfield 7.5 mi · Muskego 8.7 mi · West Allis 11 mi · Greenfield 12 mi · Wauwatosa 12 mi · Menomonee Falls 13 mi · Franklin 13 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 Waukesha (43.0117°, -88.2315°, elevation 814 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).