Watertown weather in September

In September, Watertown sees average daytime highs of 71°F and overnight lows near 50°F, with 2.5 in of rain across 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 65°F by the end. The sky is clear or mostly clear about 47% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 06 min 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 3rd-clearest and 8th-windiest month. For the whole year in context, see Watertown's year-round climate.

Daytime high
71°
4th warmest
Overnight low
50°
9th coldest
Rainfall
2.5 in
8 wet days
Daylight
12 h 18 min
6:14 AM – 6:32 PM
Cloud cover
46%
3rd clearest
Wind
10 mph
8th windiest
Solar energy
4.42 kWh/m²
Travel score
7.0
out of 10

Watertown is city in and county seat of Codington County, South Dakota, United States.

Density
329/km²
people per km²
Founded
1879

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 65°F by the end.

A typical September day in Watertown reaches about 71°F in the afternoon and slips back to 50°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 58°F and 83°F. Set against its neighbours, September runs about 8°F cooler than August and about 15°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
17656
27656
37656
47555
57555
67555
77454
87454
97353
107353
117352
127252
137251
147151
157151
167050
177050
186949
196949
206948
216848
226847
236747
246746
256746
266646
276645
286545
296544
306444

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
Jan21° / 0.95.25.490.0
Feb25° / 10°0.84.64.610.10.0
Mar38° / 21°1.663.811.60.2
Apr53° / 33°2.89.5313.23.0
May66° / 46°3.411.40.114.65.7
Jun75° / 57°4.412.2015.36.5
Jul80° / 62°3.19.4015.16.9
Aug78° / 59°3.29.3013.97.1
Sep71° / 50°2.58012.37.0
Oct56° / 37°2.26.91.210.74.1
Nov40° / 24°1.353.69.40.4
Dec26° / 13°0.955.48.70.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 47% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 15% of September, with mostly cloudy or overcast conditions the remaining 38%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16634
26634
36634
46634
56634
66436
76436
86436
96337
106337
116337
126238
136238
146139
156139
166040
176040
186040
196139
206139
216139
226139
236139
246139
256139
266139
276040
286040
295941
305941

Chance of precipitation in September

Any precipitation

Watertown gets around 2.5 in of rain over 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 27% and peaks near 28% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
126
226
326
426
526
626
726
826
926
1026
1126
1226
1327
1427
1527
1627
1728
1828
1928
2028
2128
2228
2328
2428
2528
2628
2728
2828
2927
3027

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 70% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
143222411
245212310
34721229
45021218
55320207
65520196
75520196
85819185
95919175
106218164
116318154
126617143
136717133
146817123
157216102
167216102
17741592
18751582
19771472
20781462
21801352
22821251
23841141
24861031
25861031
2687931
2790820
2890820
2991720
3092620

Wind in September

Winds average 10 mph in September.

Across September, 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.

051015151015202530
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
2411light breeze
2511light breeze
2611light breeze
2711light breeze
2811light breeze
2911light breeze
3011light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 06 min 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 90 minutes over September. Sunrise moves from 5:55 AM to 6:31 AM, and sunset from 7:01 PM to 6:05 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.15:557:01
213.05:566:59
313.05:586:57
412.95:596:55
512.96:006:54
612.86:016:52
712.86:036:50
812.76:046:48
912.76:056:46
1012.66:066:44
1112.66:076:42
1212.56:096:40
1312.56:106:38
1412.46:116:36
1512.46:126:34
1612.36:146:32
1712.36:156:30
1812.26:166:28
1912.16:176:26
2012.16:186:24
2112.06:206:22
2212.06:216:20
2311.96:226:18
2411.96:236:16
2511.86:256:14
2611.86:266:12
2711.76:276:10
2811.76:286:08
2911.66:306:06
3011.66:316:05

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.42 kWh/m².

For context, solar energy here swings from a low near 1.56 kWh/m² to a high of 6.64 kWh/m² in July across the year — September's 4.42 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.2Bright
25.2Bright
35.1Bright
45.0Bright
55.0Bright
64.9Bright
74.9Bright
84.8Bright
94.7Bright
104.7Bright
114.6Bright
124.6Bright
134.5Bright
144.4Bright
154.4Bright
164.3Bright
174.3Bright
184.2Bright
194.2Bright
204.1Bright
214.1Bright
224.0Bright
234.0Bright
244.0Moderate
253.9Moderate
263.9Moderate
273.8Moderate
283.8Moderate
293.8Moderate
303.7Moderate
Planning a trip in September

Hazard calendar for Watertown

In seasonPeak

In September, Watertown sits inside its atlantic hurricane and rainy season season. The full year is below, with each hazard's peak months called out.

Watertown sits in the Atlantic hurricane belt; the season peaks August–October.

Watertown's rainy season runs April–October, when most of the year's rain falls.

Atlantic hurricane
Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

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).

7.0
Sightseeing
2nd-best month of the year
4.5
Beach & pool
4th-best month of the year

September is one of the better times to visit Watertown for general 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 71°F and nights near 50°F. Worth packing: rain gear. About 8 days see rain.

rain gear

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 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 19UV 9Jan 1UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar4Moderate
Apr5Moderate
May6High
Jun9Very high
Jul8Very high
Aug6High
Sep6High
Oct4Moderate
Nov2Low
Dec1Low
Location & terrain

Where is Watertown?

Watertown sits at 44.9°N, 97.1°W, 1,732 ft above sea level, in United States. The nearest listed city is Brookings, 43 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 115 ft around an average of 1,736 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 344 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,237 ft.

The land around Watertown is covered by grassland (38%) and artificial surfaces (29%) within 2 miles, cropland (58%) and grassland (28%) within 10 miles, and cropland (62%) and grassland (29%) within 50 miles.

2 miles
115 ft
10 miles
344 ft
50 miles
1,237 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Brookings 43 mi · Aberdeen 78 mi · Mitchell 94 mi · Sioux Falls 96 mi · Willmar 103 mi · West Fargo 137 mi · Moorhead 137 mi · Fargo 137 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 (44.8994°, -97.1151°, elevation 1,732 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).