Southbury weather in September

In September, Southbury sees average daytime highs of 73°F and overnight lows near 57°F, with 4.1 in of rain across 9.2 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 77°F in the first days to 69°F by the end. The sky is clear or mostly clear about 37% 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 Southbury's 2nd-clearest and 9th-windiest month. For the whole year in context, see Southbury's year-round climate.

Daytime high
73°
4th warmest
Overnight low
57°
9th coldest
Rainfall
4.1 in
9.2 wet days
Daylight
12 h 18 min
5:39 AM – 5:55 PM
Cloud cover
55%
2nd clearest
Wind
6 mph
9th windiest
Solar energy
4.24 kWh/m²
Travel score
6.9
out of 10

Southbury is town in New Haven County, Connecticut, United States.

Density
191/km²
people per km²
Founded
1787

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 77°F in the first days to 69°F by the end.

A typical September day in Southbury reaches about 73°F in the afternoon and slips back to 57°F overnight — a 17°F spread between the day's warmth and the night's chill. On most days the high lands between 64°F and 82°F. Set against its neighbours, September runs about 7°F cooler than August and about 12°F warmer than October.

40°50°60°70°80°151015202530
Avg high (°F)Avg low (°F)
17861
27861
37861
47761
57760
67760
77660
87659
97659
107559
117558
127458
137458
147457
157357
167357
177356
187256
197256
207255
217155
227155
237154
247054
257053
266953
276953
286952
296852
306852

How September really feels in Southbury

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.

Southbury 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
Jan36° / 22°3.59.45.79.30.0
Feb38° / 23°3.18.85.110.30.0
Mar46° / 31°4.211.24.111.71.2
Apr58° / 41°3.811.3113.14.0
May67° / 50°3.612.1014.35.9
Jun77° / 60°4.112014.96.4
Jul82° / 65°3.911.1014.75.9
Aug80° / 64°4.310.6013.76.4
Sep73° / 57°4.19.2012.36.9
Oct62° / 46°4.29.10.210.95.3
Nov50° / 36°3.58.819.72.4
Dec40° / 28°4.210.34.39.10.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 37% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 15% of September, with mostly cloudy or overcast conditions the remaining 48%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15248
25248
35149
45248
55149
65248
75248
85347
95347
105446
115446
125446
135446
145446
155446
165446
175446
185347
195347
205248
215248
225248
235149
245149
255050
265050
275050
285149
295248
305248

Chance of precipitation in September

Any precipitation

Southbury gets around 4.1 in of rain over 9.2 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 31% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
128
228
328
429
529
629
729
830
930
1030
1130
1230
1330
1429
1529
1629
1729
1830
1930
2030
2130
2230
2330
2430
2531
2631
2731
2831
2931
3031

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 14% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1332422166
2342322165
3342321165
4352321155
5362321155
6372320154
7382320154
8392320154
9402319153
10412219143
11422218143
12442218142
13452218132
14462118132
15482117122
16492017121
17502017121
18512017111
19531916111
20541916101
21551816101
2256181691
2358181590
2460171580
2561171480
2662171470
2763161470
2865161360
2965161360
3066161260

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 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 5:23 AM to 5:54 AM, and sunset from 6:22 PM to 5:30 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:236:22
212.95:246:20
312.95:256:18
412.85:266:17
512.85:276:15
612.75:296:13
712.75:306:11
812.75:316:10
912.65:326:08
1012.65:336:06
1112.55:346:04
1212.55:356:03
1312.45:366:01
1412.45:375:59
1512.35:385:57
1612.35:395:55
1712.25:405:54
1812.25:415:52
1912.15:425:50
2012.15:435:48
2112.05:445:46
2212.05:455:45
2311.95:465:43
2411.95:475:41
2511.85:495:39
2611.85:505:37
2711.85:515:36
2811.75:525:34
2911.75:535:32
3011.65:545:30

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.24 kWh/m².

For context, solar energy here swings from a low near 1.69 kWh/m² to a high of 6.06 kWh/m² in June across the year — September's 4.24 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.8Bright
24.8Bright
34.8Bright
44.7Bright
54.7Bright
64.6Bright
74.6Bright
84.6Bright
94.5Bright
104.5Bright
114.4Bright
124.4Bright
134.4Bright
144.3Bright
154.3Bright
164.2Bright
174.2Bright
184.2Bright
194.1Bright
204.1Bright
214.0Bright
224.0Moderate
233.9Moderate
243.9Moderate
253.8Moderate
263.8Moderate
273.8Moderate
283.7Moderate
293.7Moderate
303.6Moderate
Planning a trip in September

Hazard calendar for Southbury

In seasonPeak

In September, Southbury sits inside its atlantic hurricane season. The full year is below, with each hazard's peak months called out.

Southbury sits in the Atlantic hurricane belt; the season peaks August–October.

Atlantic hurricane
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Southbury?

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

6.9
Sightseeing
1st-best month of the year
5.2
Beach & pool
4th-best month of the year

September is a reasonable time to visit Southbury for sightseeing.

What to pack for Southbury in September

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

In September, Southbury sees daytime highs around 73°F and nights near 57°F. Worth packing: light clothes and rain gear. About 9 days see rain.

light clothesrain gear

Sea temperature near Southbury in September

The nearest coast averages about 71°F in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 25 mi away) is warmest in August at about 74°F and coldest in February near 35°F.

It's comfortable for a long swim from Jul 1 to Sep 30 — about 3 months when the water holds above 68°F.

30°40°50°60°70°80°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°F)Comfort
Jan39Bracing
Feb35Bracing
Mar37Bracing
Apr44Bracing
May54Bracing
Jun65Cool
Jul72Refreshing
Aug74Refreshing
Sep71Refreshing
Oct64Cool
Nov55Bracing
Dec46Bracing

UV index in Southbury 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 Southbury peaks around July 11 at about 8 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near December 23 at about 1 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 11UV 8Dec 23UV 1
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar4Moderate
Apr6High
May8Very high
Jun7Very high
Jul8Very high
Aug5High
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low

Air quality in Southbury 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 Southbury is worst in July — around 20 µg/m³ PM2.5 (moderate), about 1.7× the cleanest month (November, 11 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateJul 1220 µg/m³Nov 1612 µg/m³
PM2.5 (µg/m³)Level
Jan13Moderate
Feb16Moderate
Mar17Moderate
Apr17Moderate
May18Moderate
Jun19Moderate
Jul20Moderate
Aug17Moderate
Sep16Moderate
Oct13Moderate
Nov11Good
Dec13Moderate
Location & terrain

Where is Southbury?

Southbury sits at 41.5°N, 73.2°W, 249 ft above sea level, in United States. The nearest listed city is Naugatuck, 8.7 mi away.

Topography around Southbury

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

Within 2 miles, the terrain around Southbury has only modest variations in elevation — a maximum elevation change of 633 ft around an average of 407 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,050 ft; within 50 miles, large variations in elevation — a maximum elevation change of 2,815 ft.

The land around Southbury is covered by trees (86%) within 2 miles, trees (85%) within 10 miles, and trees (74%) within 50 miles.

2 miles
633 ft
10 miles
1,050 ft
50 miles
2,815 ft
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Naugatuck 8.7 mi · Seymour 9.3 mi · Waterbury 9.9 mi · Ansonia 12 mi · Shelton 13 mi · Danbury 14 mi · Wolcott 14 mi · Cheshire 16 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 Southbury (41.4815°, -73.2132°, elevation 249 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. 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).