Farmington weather in September

In September, Farmington sees average daytime highs of 79°F and overnight lows near 59°F, with 3.2 in of rain across 8 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 8th-wettest month of the year here.

Highs ease over the month, from about 83°F in the first days to 75°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 12 h 54 min at the start of September to 11 h 42 min by month's end. Set against the rest of the year, September is Farmington's 1st-clearest and 10th-windiest month. For the whole year in context, see Farmington's year-round climate.

Daytime high
79°
4th warmest
Overnight low
59°
9th coldest
Rainfall
3.2 in
8 wet days
Daylight
12 h 12 min
5:49 AM – 6:03 PM
Cloud cover
46%
1st clearest
Wind
6 mph
10th windiest
Solar energy
4.76 kWh/m²
Travel score
7.1
out of 10

Farmington is city in and county seat of St. Francois County, Missouri, United States.

Density
764/km²
people per km²
Founded
1822

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 83°F in the first days to 75°F by the end.

A typical September day in Farmington reaches about 79°F in the afternoon and slips back to 59°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 69°F and 88°F. Set against its neighbours, September runs about 7°F cooler than August and about 11°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18465
28364
38364
48364
58263
68263
78262
88162
98162
108161
118061
128060
138060
147960
157959
167859
177858
187858
197858
207757
217757
227656
237656
247656
257655
267555
277554
287554
297454
307453

How September really feels in Farmington

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.

Farmington weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan41° / 26°2.88.22.69.70.1
Feb46° / 29°2.77.62.610.51.3
Mar56° / 37°4.011.21.411.73.7
Apr66° / 47°5.011.70.112.95.8
May74° / 57°4.913.20146.3
Jun83° / 66°3.711.6014.65.5
Jul87° / 69°3.511.3014.34.6
Aug86° / 67°3.09.8013.55.2
Sep79° / 59°3.28012.37.1
Oct67° / 48°3.48.40116.6
Nov55° / 37°3.68.70.6103.6
Dec44° / 29°2.88.11.99.40.9

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 16% of September, with mostly cloudy or overcast conditions the remaining 37%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16535
26535
36535
46436
56436
66436
76436
86337
96238
106238
116139
126040
136040
145941
155941
165842
175941
185941
195941
206040
216040
226139
236238
246436
256436
266634
276634
286733
296733
306832

Chance of precipitation in September

Any precipitation

Farmington gets around 3.2 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 29% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
129
229
328
428
528
627
727
826
926
1026
1126
1226
1326
1427
1527
1628
1728
1828
1929
2029
2128
2228
2328
2427
2527
2626
2725
2824
2924
3023

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 36% of days. Sticky, muggy-or-worse air turns up on roughly 26% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
11216243216
21317243215
31418233114
41619233013
51719232911
61920222810
7212122279
8222122278
9242221267
10262221257
11272221246
12292220235
13312220225
14322220224
15342220214
16362219203
17372219203
18392119192
19412118182
20432118181
21452017171
22472017161
23491916151
24511915141
25531815131
26541815130
27571714120
28581714110
29601614100
30611613100

Wind in September

Winds average 6 mph in September.

Across September, daily wind ranges from about 6 mph on the calmest days to 6 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
186calm
196calm
206calm
216calm
226calm
236calm
246calm
256calm
266calm
276calm
286calm
296calm
306calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 54 min at the start of September to 11 h 42 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 72 minutes over September. Sunrise moves from 5:36 AM to 6:01 AM, and sunset from 6:27 PM to 5:41 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:366:27
212.85:376:25
312.85:376:24
412.75:386:22
512.75:396:21
612.75:406:19
712.65:416:18
812.65:426:16
912.55:436:14
1012.55:446:13
1112.45:446:11
1212.45:456:10
1312.45:466:08
1412.35:476:06
1512.35:486:05
1612.25:496:03
1712.25:506:02
1812.25:516:00
1912.15:515:58
2012.15:525:57
2112.05:535:55
2212.05:545:53
2311.95:555:52
2411.95:565:50
2511.95:575:49
2611.85:585:47
2711.85:595:45
2811.75:595:44
2911.76:005:42
3011.76:015:41

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.76 kWh/m².

For context, solar energy here swings from a low near 1.99 kWh/m² to a high of 6.44 kWh/m² in June across the year — September's 4.76 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
144.8Bright
154.7Bright
164.7Bright
174.7Bright
184.6Bright
194.6Bright
204.6Bright
214.5Bright
224.5Bright
234.5Bright
244.5Bright
254.5Bright
264.5Bright
274.4Bright
284.4Bright
294.4Bright
304.3Bright
Planning a trip in September

Is September a good time to visit Farmington?

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

7.1
Sightseeing
1st-best month of the year
6.8
Beach & pool
2nd-best month of the year

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

What to pack for Farmington in September

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

In September, Farmington sees daytime highs around 79°F and nights near 59°F. Worth packing: light clothes, rain gear and sun protection. About 8 days see rain.

light clothesrain gearsun protection

UV index in Farmington in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Farmington peaks around June 21 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJun 21UV 10Dec 23UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar6High
Apr7Very high
May8Very high
Jun10Very high
Jul9Very high
Aug8Very high
Sep7High
Oct4Moderate
Nov4Moderate
Dec2Moderate

Air quality in Farmington 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 Farmington is worst in July — around 16 µg/m³ PM2.5 (moderate), about 2.9× the cleanest month (November, 6 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1316 µg/m³Nov 176 µg/m³
PM2.5 (µg/m³)Level
Jan6Good
Feb9Good
Mar11Good
Apr9Good
May12Good
Jun14Moderate
Jul16Moderate
Aug12Moderate
Sep10Good
Oct6Good
Nov6Good
Dec6Good
Location & terrain

Where is Farmington?

Farmington sits at 37.8°N, 90.4°W, 912 ft above sea level, in United States. The nearest listed city is Arnold, 45 mi away.

Topography around Farmington

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

Within 2 miles, the terrain around Farmington has only modest variations in elevation — a maximum elevation change of 361 ft around an average of 922 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,014 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,562 ft.

The land around Farmington is covered by grassland (42%) and trees (34%) within 2 miles, trees (63%) and grassland (31%) within 10 miles, and trees (73%) within 50 miles.

2 miles
361 ft
10 miles
1,014 ft
50 miles
1,562 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Arnold 45 mi · Oakville 48 mi · Mehlville 50 mi · Concord 52 mi · Lemay 53 mi · Affton 53 mi · Kirkwood 55 mi · Webster Groves 56 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 Farmington (37.7809°, -90.4218°, elevation 912 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).