Ottumwa weather in September

In September, Ottumwa sees average daytime highs of 76°F and overnight lows near 56°F, with 3.6 in of rain across 8.1 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 4th-wettest month of the year here.

Highs ease over the month, from about 80°F in the first days to 71°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 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Ottumwa's 1st-clearest and 9th-windiest month. For the whole year in context, see Ottumwa's year-round climate.

Daytime high
76°
4th warmest
Overnight low
56°
9th coldest
Rainfall
3.6 in
8.1 wet days
Daylight
12 h 18 min
5:56 AM – 6:12 PM
Cloud cover
45%
1st clearest
Wind
8 mph
9th windiest
Solar energy
4.7 kWh/m²
Travel score
7.2
out of 10

Ottumwa is city in and the county seat of Wapello County, Iowa, United States.

Density
575/km²
people per km²
Founded
1844

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 80°F in the first days to 71°F by the end.

A typical September day in Ottumwa reaches about 76°F in the afternoon and slips back to 56°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 65°F and 87°F. Set against its neighbours, September runs about 7°F cooler than August and about 12°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18162
28161
38061
48060
58060
68060
77959
87959
97858
107858
117858
127757
137757
147656
157656
167656
177555
187555
197554
207454
217454
227453
237353
247352
257352
267252
277251
287151
297150
307150

How September really feels in Ottumwa

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.

Ottumwa weather by month

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

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan32° / 16°1.46.84.59.40.0
Feb36° / 20°1.874.310.40.0
Mar49° / 31°2.792.511.72.1
Apr62° / 42°4.311.60.813.14.9
May72° / 53°4.812.70.114.36.2
Jun81° / 63°5.011.8014.96.0
Jul85° / 67°3.39.6014.65.4
Aug83° / 64°3.59.4013.66.2
Sep76° / 56°3.68.1012.37.2
Oct64° / 44°2.87.90.210.95.9
Nov49° / 32°2.26.71.29.72.2
Dec37° / 22°1.86.33.59.10.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 47% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 14% of September, with mostly cloudy or overcast conditions the remaining 38%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16436
26535
36634
46535
56634
66535
76535
86535
96436
106337
116337
126238
136139
146139
156040
165941
175941
185842
195941
205941
215941
225941
235941
246040
256040
266040
276040
286040
296040
306139

Chance of precipitation in September

Any precipitation

Ottumwa gets around 3.6 in of rain over 8.1 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 28% and peaks near 30% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
128
228
328
428
528
628
728
828
928
1029
1129
1230
1330
1430
1530
1630
1730
1830
1929
2029
2129
2228
2328
2427
2527
2626
2726
2826
2925
3025

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 47% of days. Sticky, muggy-or-worse air turns up on roughly 17% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
12022222610
2222222259
3242322248
4262322227
5282322217
6302321206
7322321195
8342320185
9362220174
10382219174
11402219163
12422218163
13442217152
14452116152
15472116142
16492115141
17512114131
18522113131
19542112121
20562111111
21572111111
22602010100
236220990
246320980
256519880
266619870
276818860
286918760
297117750
307217650

Wind in September

Winds average 8 mph in September.

Across September, daily wind ranges from about 7 mph on the calmest days to 9 mph at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (mph)Feels
17calm
27light breeze
38light breeze
48light breeze
58light breeze
68light breeze
78light breeze
88light breeze
98light breeze
108light breeze
118light breeze
128light breeze
138light breeze
148light breeze
158light breeze
168light breeze
178light breeze
188light breeze
198light breeze
208light breeze
218light breeze
228light breeze
239light breeze
249light breeze
259light breeze
269light breeze
279light breeze
289light breeze
299light breeze
309light 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 5:41 AM to 6:11 AM, and sunset from 6:38 PM to 5:47 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:416:38
212.95:426:36
312.95:436:35
412.85:446:33
512.85:456:31
612.75:466:30
712.75:476:28
812.65:486:26
912.65:496:24
1012.55:506:23
1112.55:516:21
1212.55:526:19
1312.45:536:17
1412.45:546:16
1512.35:556:14
1612.35:566:12
1712.25:576:10
1812.25:586:08
1912.15:596:07
2012.16:006:05
2112.06:016:03
2212.06:026:01
2311.96:036:00
2411.96:045:58
2511.86:055:56
2611.86:065:54
2711.86:075:53
2811.76:085:51
2911.76:095:49
3011.66:115:47

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.7 kWh/m².

For context, solar energy here swings from a low near 1.82 kWh/m² to a high of 6.44 kWh/m² in July across the year — September's 4.7 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.3Bright
25.2Bright
35.2Bright
45.2Bright
55.1Bright
65.1Bright
75.0Bright
85.0Bright
95.0Bright
104.9Bright
114.9Bright
124.8Bright
134.8Bright
144.7Bright
154.7Bright
164.6Bright
174.6Bright
184.5Bright
194.5Bright
204.5Bright
214.4Bright
224.4Bright
234.3Bright
244.3Bright
254.3Bright
264.2Bright
274.2Bright
284.1Bright
294.1Bright
304.0Bright
Planning a trip in September

Is September a good time to visit Ottumwa?

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

7.2
Sightseeing
1st-best month of the year
6.1
Beach & pool
4th-best month of the year

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

What to pack for Ottumwa in September

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

In September, Ottumwa sees daytime highs around 76°F and nights near 56°F. Worth packing: light clothes, rain gear and sun protection. About 8 days see rain.

light clothesrain gearsun protection

UV index in Ottumwa 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 Ottumwa peaks around June 20 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 2 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJun 20UV 9Dec 19UV 2
UV index (midday)Level
Jan2Moderate
Feb3Moderate
Mar4Moderate
Apr6High
May7Very high
Jun10Very high
Jul9Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Ottumwa 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 Ottumwa is worst in July — around 17 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (October, 7 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateGoodJul 1816 µg/m³Oct 217 µg/m³
PM2.5 (µg/m³)Level
Jan12Good
Feb14Moderate
Mar13Moderate
Apr11Good
May12Moderate
Jun13Moderate
Jul17Moderate
Aug14Moderate
Sep12Good
Oct7Good
Nov8Good
Dec10Good
Location & terrain

Where is Ottumwa?

Ottumwa sits at 41.0°N, 92.4°W, 673 ft above sea level, in United States. The nearest listed city is Newton, 57 mi away.

Topography around Ottumwa

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

Within 2 miles, the terrain around Ottumwa has only modest variations in elevation — a maximum elevation change of 249 ft around an average of 715 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 322 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 574 ft.

The land around Ottumwa is covered by trees (45%), artificial surfaces (25%) and grassland (20%) within 2 miles, cropland (40%), trees (33%) and grassland (24%) within 10 miles, and cropland (52%), grassland (25%) and trees (22%) within 50 miles.

2 miles
249 ft
10 miles
322 ft
50 miles
574 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Newton 57 mi · Kirksville 58 mi · Coralville 63 mi · Iowa City 63 mi · Indianola 64 mi · North Liberty 66 mi · Burlington 70 mi · Altoona 70 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 Ottumwa (41.02°, -92.4113°, elevation 673 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).