Frankfort weather in September

In September, Frankfort sees average daytime highs of 77°F and overnight lows near 57°F, with 2.7 in of rain across 8.1 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 80°F in the first days to 72°F by the end. The sky is clear or mostly clear about 42% 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 Frankfort's 1st-clearest and 9th-windiest month. For the whole year in context, see Frankfort's year-round climate.

Daytime high
77°
4th warmest
Overnight low
57°
9th coldest
Rainfall
2.7 in
8.1 wet days
Daylight
12 h 18 min
6:33 AM – 6:48 PM
Cloud cover
50%
1st clearest
Wind
8 mph
9th windiest
Solar energy
4.58 kWh/m²
Travel score
7.2
out of 10

Frankfort is county seat in Clinton County, Indiana, United States.

Density
982/km²
people per km²
Founded
1830

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 72°F by the end.

A typical September day in Frankfort reaches about 77°F in the afternoon and slips back to 57°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 66°F and 87°F. Set against its neighbours, September runs about 5°F cooler than August and about 12°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18162
28162
38062
48061
58061
68060
78060
87960
97959
107959
117859
127858
137858
147757
157757
167756
177656
187656
197655
207555
217555
227454
237454
247453
257353
267353
277352
287252
297251
307151

How September really feels in Frankfort

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.

Frankfort 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°3.09.54.99.50.0
Feb39° / 24°2.48.74.410.40.1
Mar50° / 32°3.510.82.411.72.1
Apr62° / 43°4.412.10.4135.0
May72° / 54°4.513.6014.26.1
Jun80° / 63°4.312.3014.86.1
Jul83° / 66°3.411.2014.65.7
Aug82° / 64°3.09.6013.66.5
Sep77° / 57°2.78.1012.37.2
Oct64° / 46°3.29.10.110.95.8
Nov50° / 35°3.49.11.29.82.4
Dec39° / 26°2.79.73.79.20.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 42% 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 42%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15941
25941
35941
45941
56040
66040
76040
86040
96040
106040
116040
125941
135941
145842
155743
165743
175743
185743
195743
205644
215644
225644
235743
245743
255644
265644
275644
285743
295743
305743

Chance of precipitation in September

Any precipitation

Frankfort gets around 2.7 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 29% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
128
228
327
427
527
627
727
826
926
1026
1126
1226
1326
1426
1527
1627
1727
1827
1928
2028
2128
2229
2329
2429
2529
2629
2729
2829
2929
3029

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 15% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1232024267
2252023256
3262123256
4282122245
5302122234
6322122213
7342221203
8362221192
9382221182
10402220172
11412220161
12432120151
13452119141
14472119131
15482019121
16502018111
17531918100
1855191790
1958181680
2058181680
2161171570
2262171470
2365161360
2466161260
2567151260
2669151150
2769151150
2871141050
2972141040
3072141040

Wind in September

Winds average 8 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
147light breeze
157light breeze
168light 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 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 6:18 AM to 6:47 AM, and sunset from 7:14 PM to 6:24 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.96:187:14
212.96:197:12
312.86:207:10
412.86:217:09
512.86:227:07
612.76:237:05
712.76:247:04
812.66:257:02
912.66:267:00
1012.56:276:59
1112.56:286:57
1212.46:296:55
1312.46:306:53
1412.46:316:52
1512.36:326:50
1612.36:336:48
1712.26:346:46
1812.26:346:45
1912.16:356:43
2012.16:366:41
2112.06:376:40
2212.06:386:38
2311.96:396:36
2411.96:416:34
2511.96:426:33
2611.86:436:31
2711.86:446:29
2811.76:456:27
2911.76:466:26
3011.66:476:24

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.58 kWh/m².

For context, solar energy here swings from a low near 1.71 kWh/m² to a high of 6.33 kWh/m² in July across the year — September's 4.58 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.1Bright
25.1Bright
35.0Bright
45.0Bright
55.0Bright
64.9Bright
74.9Bright
84.8Bright
94.8Bright
104.8Bright
114.7Bright
124.7Bright
134.7Bright
144.6Bright
154.6Bright
164.5Bright
174.5Bright
184.5Bright
194.4Bright
204.4Bright
214.3Bright
224.3Bright
234.3Bright
244.2Bright
254.2Bright
264.2Bright
274.1Bright
284.1Bright
294.0Bright
304.0Moderate
Planning a trip in September

Is September a good time to visit Frankfort?

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
6.2
Beach & pool
3rd-best month of the year

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

What to pack for Frankfort in September

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

In September, Frankfort sees daytime highs around 77°F and nights near 57°F. Worth packing: light clothes, rain gear and sun protection. About 8 days see rain.

light clothesrain gearsun protection

UV index in Frankfort 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 Frankfort peaks around June 23 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 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 23UV 9Dec 22UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov3Moderate
Dec2Low

Air quality in Frankfort 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 Frankfort 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).

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateModerateGoodJul 1416 µg/m³Oct 218 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb12Moderate
Mar12Moderate
Apr12Good
May13Moderate
Jun15Moderate
Jul16Moderate
Aug14Moderate
Sep11Good
Oct7Good
Nov8Good
Dec9Good
Location & terrain

Where is Frankfort?

Frankfort sits at 40.3°N, 86.5°W, 850 ft above sea level, in United States. The nearest listed city is Lebanon, 16 mi away.

Topography around Frankfort

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

Within 2 miles, the terrain around Frankfort has only modest variations in elevation — a maximum elevation change of 98 ft around an average of 856 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 282 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 627 ft.

The land around Frankfort is covered by cropland (44%) within 2 miles, cropland (81%) within 10 miles, and cropland (70%) within 50 miles.

2 miles
98 ft
10 miles
282 ft
50 miles
627 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Lebanon 16 mi · Lafayette 21 mi · West Lafayette 23 mi · Kokomo 24 mi · Crawfordsville 25 mi · Westfield 26 mi · Zionsville 26 mi · Carmel 29 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 Frankfort (40.2795°, -86.5108°, elevation 850 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).