Mount Vernon weather in September

In September, Mount Vernon sees average daytime highs of 74°F and overnight lows near 56°F, with 3.0 in of rain across 9 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 11th-wettest month of the year here.

Highs ease over the month, from about 78°F in the first days to 70°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 12 h 54 min at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Mount Vernon's 1st-clearest and 10th-windiest month. For the whole year in context, see Mount Vernon's year-round climate.

Daytime high
74°
4th warmest
Overnight low
56°
9th coldest
Rainfall
3.0 in
9 wet days
Daylight
12 h 18 min
6:16 AM – 6:32 PM
Cloud cover
52%
1st clearest
Wind
6 mph
10th windiest
Solar energy
4.4 kWh/m²
Travel score
7.0
out of 10

Mount Vernon is city in Knox County, Ohio, United States.

Density
674/km²
people per km²
Founded
1805

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 78°F in the first days to 70°F by the end.

A typical September day in Mount Vernon reaches about 74°F in the afternoon and slips back to 56°F overnight — a 18°F spread between the day's warmth and the night's chill. On most days the high lands between 64°F and 84°F. Set against its neighbours, September runs about 6°F cooler than August and about 12°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
17961
27861
37860
47860
57860
67760
77759
87759
97658
107658
117658
127657
137557
147556
157456
167456
177455
187455
197355
207354
217254
227253
237253
247153
257152
267052
277052
287051
296951
306950

How September really feels in Mount Vernon

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.

Mount Vernon weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan35° / 21°3.311.46.99.40.0
Feb38° / 23°2.69.45.210.40.0
Mar48° / 31°3.811.73.611.71.6
Apr61° / 42°4.612.91.1134.5
May70° / 52°4.413.7014.25.9
Jun79° / 61°4.212.1014.86.3
Jul82° / 65°3.611.5014.66.2
Aug80° / 63°3.110.4013.66.5
Sep74° / 56°3.09012.37.0
Oct62° / 45°3.19.90.110.95.3
Nov49° / 35°3.29.81.79.82.0
Dec39° / 27°3.310.14.59.20.1

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 (%)
15842
25842
35842
45842
55842
65842
75743
85743
95644
105644
115644
125545
135545
145446
155446
165446
175446
185446
195446
205347
215446
225446
235446
245446
255347
265347
275446
285347
295347
305248

Chance of precipitation in September

Any precipitation

Mount Vernon gets around 3.0 in of rain over 9 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 (%)
129
229
329
429
529
629
729
828
928
1028
1128
1229
1329
1429
1529
1630
1730
1830
1931
2031
2131
2232
2332
2432
2533
2633
2733
2833
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 49% 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 (%)
1272422234
2282422224
3292522213
4312521203
5322521193
6342520182
7362520172
8372519162
9392519162
10402518151
11412518141
12432518131
13442517131
14462517121
15482416110
16502416110
17522315100
1854231490
1955221490
2058211380
2159201380
2262191270
2362191270
2465181160
2566171160
2667171060
2769161050
287016950
297115950
307115950

Wind in September

Winds average 6 mph in September.

Across September, daily wind ranges from about 6 mph on the calmest days to 7 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
96calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
176calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277calm
287calm
297calm
307calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 54 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 78 minutes over September. Sunrise moves from 6:01 AM to 6:31 AM, and sunset from 6:58 PM to 6:08 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.96:016:58
212.96:026:56
312.96:036:54
412.86:046:53
512.86:056:51
612.76:066:49
712.76:076:48
812.66:086:46
912.66:096:44
1012.56:106:43
1112.56:116:41
1212.46:126:39
1312.46:136:37
1412.46:146:36
1512.36:156:34
1612.36:166:32
1712.26:176:30
1812.26:186:29
1912.16:196:27
2012.16:206:25
2112.06:216:23
2212.06:226:22
2311.96:236:20
2411.96:246:18
2511.96:256:17
2611.86:266:15
2711.86:276:13
2811.76:286:11
2911.76:306:10
3011.66:316:08

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.4 kWh/m².

For context, solar energy here swings from a low near 1.55 kWh/m² to a high of 6.17 kWh/m² in June across the year — September's 4.4 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
15.0Bright
24.9Bright
34.9Bright
44.8Bright
54.8Bright
64.8Bright
74.7Bright
84.7Bright
94.7Bright
104.6Bright
114.6Bright
124.6Bright
134.5Bright
144.5Bright
154.4Bright
164.4Bright
174.4Bright
184.3Bright
194.3Bright
204.2Bright
214.2Bright
224.1Bright
234.1Bright
244.0Bright
254.0Bright
264.0Moderate
273.9Moderate
283.9Moderate
293.8Moderate
303.8Moderate
Planning a trip in September

Is September a good time to visit Mount Vernon?

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

7.0
Sightseeing
1st-best month of the year
5.5
Beach & pool
4th-best month of the year

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

What to pack for Mount Vernon in September

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

In September, Mount Vernon sees daytime highs around 74°F and nights near 56°F. Worth packing: light clothes and rain gear. About 9 days see rain.

light clothesrain gear

UV index in Mount Vernon 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 Mount Vernon peaks around June 20 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJun 20UV 9Dec 23UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun10Very high
Jul9Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov3Moderate
Dec2Low

Air quality in Mount Vernon 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 Mount Vernon 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).

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1216 µg/m³Oct 247 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb11Good
Mar11Good
Apr11Good
May14Moderate
Jun15Moderate
Jul16Moderate
Aug14Moderate
Sep11Good
Oct7Good
Nov7Good
Dec8Good
Location & terrain

Where is Mount Vernon?

Mount Vernon sits at 40.4°N, 82.5°W, 1,001 ft above sea level, in United States. The nearest listed city is Newark, 24 mi away.

Topography around Mount Vernon

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

Within 2 miles, the terrain around Mount Vernon has only modest variations in elevation — a maximum elevation change of 312 ft around an average of 1,040 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 597 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,033 ft.

The land around Mount Vernon is covered by trees (34%) and grassland (31%) within 2 miles, trees (38%), cropland (38%) and grassland (21%) within 10 miles, and trees (40%) and cropland (37%) within 50 miles.

2 miles
312 ft
10 miles
597 ft
50 miles
1,033 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Newark 24 mi · Mansfield 25 mi · Pataskala 29 mi · Westerville 30 mi · Delaware 31 mi · Gahanna 33 mi · Ashland 34 mi · Reynoldsburg 35 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 Mount Vernon (40.3934°, -82.4857°, elevation 1,001 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).