Marshalltown weather in September

In September, Marshalltown sees average daytime highs of 74°F and overnight lows near 54°F, with 3.7 in of rain across 8.4 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 79°F in the first days to 70°F by the end. The sky is clear or mostly clear about 46% 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 Marshalltown's 1st-clearest and 9th-windiest month. For the whole year in context, see Marshalltown's year-round climate.

Daytime high
74°
4th warmest
Overnight low
54°
9th coldest
Rainfall
3.7 in
8.4 wet days
Daylight
12 h 18 min
5:58 AM – 6:14 PM
Cloud cover
46%
1st clearest
Wind
9 mph
9th windiest
Solar energy
4.59 kWh/m²
Travel score
7.2
out of 10

Marshalltown is city and the county seat of Marshall County, Iowa, United States.

Density
552/km²
people per km²
Founded
1853

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 79°F in the first days to 70°F by the end.

A typical September day in Marshalltown reaches about 74°F in the afternoon and slips back to 54°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 63°F and 85°F. Set against its neighbours, September runs about 6°F cooler than August and about 13°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
17960
27959
37959
47858
57858
67858
77757
87757
97757
107656
117656
127655
137555
147555
157454
167454
177453
187353
197353
207352
217252
227251
237151
247151
257150
267050
277049
287049
296949
306948

How September really feels in Marshalltown

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.

Marshalltown 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° / 13°1.36.54.99.30.0
Feb33° / 16°1.56.44.710.30.0
Mar46° / 28°2.58.62.911.71.5
Apr60° / 40°4.511.5113.14.5
May70° / 51°5.313.50.114.36.0
Jun79° / 62°5.211.80156.3
Jul82° / 65°3.810.1014.76.3
Aug80° / 62°3.99.1013.76.8
Sep74° / 54°3.78.4012.37.2
Oct61° / 42°2.97.90.410.95.4
Nov46° / 29°2.16.71.69.61.5
Dec33° / 19°1.66.34.790.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 46% 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 40%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16733
26733
36634
46634
56634
66535
76535
86436
96337
106238
116139
126139
136040
145842
155842
165743
175644
185644
195644
205644
215644
225644
235644
245743
255743
265743
275743
285842
295842
305842

Chance of precipitation in September

Any precipitation

Marshalltown gets around 3.7 in of rain over 8.4 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 (%)
126
226
326
426
526
626
727
827
928
1028
1128
1229
1329
1430
1530
1630
1730
1830
1930
2030
2130
2229
2329
2429
2529
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 53% of days. Sticky, muggy-or-worse air turns up on roughly 13% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1252323228
2272322207
3292422197
4312421176
5332420166
6362420155
7382419145
8402418134
9422418134
10432417123
11452416123
12472316122
13492315112
14502215112
15522214111
16542114101
17552113101
18572012101
1959191291
2060191191
2164181080
2264181080
236717970
246816970
257016860
267215850
277414750
287514740
297713640
307713640

Wind in September

Winds average 9 mph in September.

Across September, daily wind ranges from about 8 mph on the calmest days to 10 mph at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (mph)Feels
18light breeze
28light breeze
38light breeze
48light breeze
58light breeze
68light breeze
78light breeze
88light breeze
98light breeze
109light breeze
119light breeze
129light breeze
139light breeze
149light breeze
159light breeze
169light breeze
179light breeze
189light breeze
199light breeze
209light breeze
219light breeze
229light breeze
239light breeze
249light breeze
259light breeze
269light breeze
279light breeze
289light breeze
299light breeze
3010light 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 6:13 AM, and sunset from 6:41 PM to 5:49 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:416:41
212.95:436:39
312.95:446:38
412.95:456:36
512.85:466:34
612.85:476:32
712.75:486:31
812.75:496:29
912.65:506:27
1012.65:516:25
1112.55:526:23
1212.55:536:22
1312.45:546:20
1412.45:556:18
1512.35:576:16
1612.35:586:14
1712.25:596:12
1812.26:006:11
1912.16:016:09
2012.16:026:07
2112.06:036:05
2212.06:046:03
2311.96:056:02
2411.96:066:00
2511.86:075:58
2611.86:085:56
2711.76:105:54
2811.76:115:53
2911.66:125:51
3011.66:135:49

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.59 kWh/m².

For context, solar energy here swings from a low near 1.76 kWh/m² to a high of 6.44 kWh/m² in July across the year — September's 4.59 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.2Bright
25.2Bright
35.1Bright
45.1Bright
55.1Bright
65.0Bright
75.0Bright
84.9Bright
94.9Bright
104.8Bright
114.8Bright
124.7Bright
134.7Bright
144.6Bright
154.6Bright
164.5Bright
174.5Bright
184.4Bright
194.4Bright
204.3Bright
214.3Bright
224.2Bright
234.2Bright
244.1Bright
254.1Bright
264.1Bright
274.0Bright
284.0Moderate
293.9Moderate
303.9Moderate
Planning a trip in September

Is September a good time to visit Marshalltown?

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
5.6
Beach & pool
4th-best month of the year

September is one of the better times to visit Marshalltown for general sightseeing.

What to pack for Marshalltown in September

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

In September, Marshalltown sees daytime highs around 74°F and nights near 54°F. Worth packing: light clothes, rain gear and sun protection. About 8 days see rain.

light clothesrain gearsun protection

UV index in Marshalltown 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 Marshalltown peaks around June 18 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 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 18UV 9Dec 21UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar4Moderate
Apr6High
May7Very high
Jun9Very high
Jul8Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Marshalltown 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 Marshalltown is worst in July — around 16 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (October, 7 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateGoodJul 1916 µg/m³Oct 218 µg/m³
PM2.5 (µg/m³)Level
Jan13Moderate
Feb15Moderate
Mar14Moderate
Apr11Good
May12Good
Jun13Moderate
Jul16Moderate
Aug15Moderate
Sep12Good
Oct7Good
Nov9Good
Dec10Good
Location & terrain

Where is Marshalltown?

Marshalltown sits at 42.0°N, 92.9°W, 942 ft above sea level, in United States. The nearest listed city is Newton, 25 mi away.

Topography around Marshalltown

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

Within 2 miles, the terrain around Marshalltown has only modest variations in elevation — a maximum elevation change of 161 ft around an average of 902 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 266 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 620 ft.

The land around Marshalltown is covered by grassland (29%), artificial surfaces (29%) and trees (22%) within 2 miles, cropland (74%) within 10 miles, and cropland (80%) within 50 miles.

2 miles
161 ft
10 miles
266 ft
50 miles
620 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Newton 25 mi · Ames 37 mi · Altoona 40 mi · Cedar Falls 40 mi · Waterloo 42 mi · Ankeny 42 mi · Des Moines 48 mi · Johnston 48 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 Marshalltown (42.0494°, -92.908°, elevation 942 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).