Watertown weather in September

In September, Watertown sees average daytime highs of 72°F and overnight lows near 53°F, with 2.9 in of rain across 8.8 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 Watertown's 1st-clearest and 9th-windiest month. For the whole year in context, see Watertown's year-round climate.

Daytime high
72°
4th warmest
Overnight low
53°
9th coldest
Rainfall
2.9 in
8.8 wet days
Daylight
12 h 18 min
5:41 AM – 5:58 PM
Cloud cover
52%
1st clearest
Wind
7 mph
9th windiest
Solar energy
4.27 kWh/m²
Travel score
6.9
out of 10

Watertown is city in Dodge County and Jefferson County, Wisconsin, United States.

Density
739/km²
people per km²

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 Watertown reaches about 72°F in the afternoon and slips back to 53°F overnight — a 19°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)
17758
27658
37658
47658
57657
67557
77556
87456
97456
107455
117355
127355
137354
147254
157253
167253
177153
187152
197052
207051
216951
226951
236950
246850
256849
266749
276749
286748
296648
306647

How September really feels in Watertown

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.

Watertown 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
Jan27° / 13°1.67.96.69.20.0
Feb31° / 16°1.66.95.510.20.0
Mar43° / 26°2.38.93.911.60.8
Apr56° / 38°3.712.11.913.13.5
May67° / 49°3.711.8014.45.8
Jun77° / 59°3.911.2015.16.6
Jul81° / 63°3.29.9014.96.6
Aug79° / 61°3.510.2013.86.8
Sep72° / 53°2.98.8012.36.9
Oct58° / 42°2.890.310.84.5
Nov44° / 30°2.17.929.50.9
Dec32° / 20°1.97.65.48.90.0

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 15% of September, with mostly cloudy or overcast conditions the remaining 46%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15842
25842
35842
45842
55941
65842
75842
85743
95743
105644
115545
125545
135446
145347
155347
165347
175248
185248
195248
205248
215248
225248
235248
245248
255149
265149
275149
285149
295149
305149

Chance of precipitation in September

Any precipitation

Watertown gets around 2.9 in of rain over 8.8 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 33% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
128
228
327
427
527
627
727
827
927
1028
1128
1229
1330
1430
1531
1631
1732
1832
1932
2032
2132
2233
2333
2433
2533
2633
2733
2832
2932
3032

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 58% of days. Sticky, muggy-or-worse air turns up on roughly 9% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1332423173
2352422163
3372422153
4392321142
5412321132
6422320132
7442320122
8462219121
9472219111
10492218111
11512117101
12512117101
1353211691
1454201691
1557201580
1659191480
1760191470
1862181370
1964181260
2066171160
2168161150
2270151050
2372141040
247413940
257513840
267712830
277811830
287911730
298110720
30839620

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
157light breeze
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 5:24 AM to 5:57 AM, and sunset from 6:26 PM to 5:32 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:246:26
213.05:256:24
312.95:266:22
412.95:276:20
512.85:286:18
612.85:296:17
712.75:306:15
812.75:316:13
912.65:336:11
1012.65:346:09
1112.55:356:07
1212.55:366:05
1312.45:376:04
1412.45:386:02
1512.35:396:00
1612.35:415:58
1712.25:425:56
1812.25:435:54
1912.15:445:52
2012.15:455:50
2112.05:465:49
2212.05:475:47
2311.95:495:45
2411.95:505:43
2511.85:515:41
2611.85:525:39
2711.75:535:37
2811.75:545:35
2911.65:565:34
3011.65:575:32

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.27 kWh/m².

For context, solar energy here swings from a low near 1.54 kWh/m² to a high of 6.3 kWh/m² in June across the year — September's 4.27 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
154.2Bright
164.2Bright
174.2Bright
184.1Bright
194.1Bright
204.0Bright
214.0Bright
224.0Moderate
233.9Moderate
243.9Moderate
253.9Moderate
263.8Moderate
273.8Moderate
283.7Moderate
293.7Moderate
303.6Moderate
Planning a trip in September

Is September a good time to visit Watertown?

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
4.7
Beach & pool
4th-best month of the year

September is a reasonable time to visit Watertown for sightseeing.

What to pack for Watertown in September

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

In September, Watertown sees daytime highs around 72°F and nights near 53°F. Worth packing: light clothes and rain gear. About 9 days see rain.

light clothesrain gear

Sea temperature near Watertown 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 44 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 Watertown 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 Watertown 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 Watertown 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 Watertown is worst in July — around 15 µg/m³ PM2.5 (moderate), about 2.0× the cleanest month (November, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateModerateGoodJul 1415 µg/m³Nov 118 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb12Moderate
Mar13Moderate
Apr12Good
May13Moderate
Jun14Moderate
Jul15Moderate
Aug14Moderate
Sep11Good
Oct8Good
Nov8Good
Dec9Good
Location & terrain

Where is Watertown?

Watertown sits at 43.2°N, 88.7°W, 853 ft above sea level, in United States. The nearest listed city is Oconomowoc, 13 mi away.

Topography around Watertown

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

Within 2 miles, the terrain around Watertown has only modest variations in elevation — a maximum elevation change of 180 ft around an average of 843 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 325 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,129 ft.

The land around Watertown is covered by grassland (28%), artificial surfaces (27%) and trees (26%) within 2 miles, cropland (57%) and trees (21%) within 10 miles, and cropland (47%) and trees (26%) within 50 miles.

2 miles
180 ft
10 miles
325 ft
50 miles
1,129 ft
treesgrasslandcroplandartificial surfacesbare terrainwaterwetland
September weather nearby: Oconomowoc 13 mi · Beaver Dam 19 mi · Sun Prairie 24 mi · Waukesha 28 mi · Menomonee Falls 31 mi · Germantown 31 mi · West Bend 32 mi · Brookfield 33 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 Watertown (43.1947°, -88.729°, elevation 853 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).