Danbury weather in September

In September, Danbury sees average daytime highs of 73°F and overnight lows near 56°F, with 4.3 in of rain across 9.4 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 4th-wettest month of the year here.

Highs ease over the month, from about 77°F in the first days to 68°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 Danbury's 1st-clearest and 9th-windiest month. For the whole year in context, see Danbury's year-round climate.

Daytime high
73°
4th warmest
Overnight low
56°
9th coldest
Rainfall
4.3 in
9.4 wet days
Daylight
12 h 18 min
5:40 AM – 5:56 PM
Cloud cover
55%
1st clearest
Wind
6 mph
9th windiest
Solar energy
4.2 kWh/m²
Travel score
6.9
out of 10

Danbury is city in Fairfield County, Connecticut, United States.

Density
740/km²
people per km²
Founded
1702

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 68°F by the end.

A typical September day in Danbury reaches about 73°F in the afternoon and slips back to 56°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°60°80°151015202530
Avg high (°F)Avg low (°F)
17861
27861
37760
47760
57760
67660
77659
87659
97659
107558
117558
127458
137457
147457
157356
167356
177356
187255
197255
207255
217154
227154
237054
247053
257053
266953
276952
286852
296851
306851

How September really feels in Danbury

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.

Danbury weather by month

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

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan35° / 21°3.59.45.79.40.0
Feb38° / 22°3.08.74.910.30.0
Mar46° / 30°4.211.14.211.71.2
Apr58° / 40°3.811.30.913.14.1
May68° / 50°3.912014.35.9
Jun77° / 60°4.412014.96.4
Jul82° / 65°4.311.3014.75.9
Aug80° / 64°4.510.9013.76.4
Sep73° / 56°4.39.4012.36.9
Oct61° / 45°4.29.40.210.95.2
Nov50° / 35°3.48.71.29.72.3
Dec40° / 27°4.110.54.59.10.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 37% 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 47%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15248
25248
35248
45248
55248
65347
75347
85347
95446
105446
115446
125644
135545
145545
155545
165545
175545
185446
195446
205347
215347
225248
235149
245149
255050
265050
275050
285050
295149
305149

Chance of precipitation in September

Any precipitation

Danbury gets around 4.3 in of rain over 9.4 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 30% and peaks near 32% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
128
228
329
429
529
630
730
830
930
1031
1131
1231
1331
1431
1530
1630
1730
1830
1930
2030
2131
2231
2331
2431
2531
2631
2731
2831
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 48% 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 (%)
1312522175
2322522165
3332422165
4342422155
5352421155
6362421154
7372420144
8382420144
9392420143
10402419143
11412419133
12432319133
13442318132
14452318122
15472218122
16482218111
17492118101
18502118101
1953201791
2053201791
2156191780
2257191680
2359181670
2459181670
2562171560
2662171560
2764171450
2866161350
2966161350
3068161240

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 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 5:24 AM to 5:55 AM, and sunset from 6:23 PM to 5:31 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:246:23
212.95:256:21
312.95:266:19
412.85:276:18
512.85:296:16
612.75:306:14
712.75:316:12
812.65:326:11
912.65:336:09
1012.65:346:07
1112.55:356:05
1212.55:366:03
1312.45:376:02
1412.45:386:00
1512.35:395:58
1612.35:405:56
1712.25:415:55
1812.25:425:53
1912.15:435:51
2012.15:445:49
2112.05:455:47
2212.05:465:46
2311.95:475:44
2411.95:485:42
2511.85:495:40
2611.85:515:38
2711.85:525:37
2811.75:535:35
2911.75:545:33
3011.65:555:31

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.2 kWh/m².

For context, solar energy here swings from a low near 1.67 kWh/m² to a high of 6 kWh/m² in June across the year — September's 4.2 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.8Bright
24.8Bright
34.7Bright
44.7Bright
54.6Bright
64.6Bright
74.5Bright
84.5Bright
94.5Bright
104.4Bright
114.4Bright
124.3Bright
134.3Bright
144.3Bright
154.2Bright
164.2Bright
174.2Bright
184.1Bright
194.1Bright
204.0Bright
214.0Moderate
223.9Moderate
233.9Moderate
243.9Moderate
253.8Moderate
263.8Moderate
273.7Moderate
283.7Moderate
293.6Moderate
303.6Moderate
Planning a trip in September

Hazard calendar for Danbury

In seasonPeak

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

Danbury 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 Danbury?

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 Danbury for sightseeing.

What to pack for Danbury in September

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

In September, Danbury sees daytime highs around 73°F and nights near 56°F. Worth packing: light clothes and rain gear. About 9 days see rain.

light clothesrain gear

Sea temperature near Danbury 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 19 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 Jun 30 to Sep 30 — about 3.1 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
May55Bracing
Jun65Cool
Jul72Refreshing
Aug74Refreshing
Sep71Refreshing
Oct64Cool
Nov55Bracing
Dec46Bracing

UV index in Danbury 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 Danbury 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
Mar5Moderate
Apr6High
May7Very high
Jun8Very high
Jul8Very high
Aug6High
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low

Air quality in Danbury 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 Danbury 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 Danbury?

Danbury sits at 41.4°N, 73.5°W, 397 ft above sea level, in United States. The nearest listed city is Wilton, 14 mi away.

Topography around Danbury

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

Within 2 miles, the terrain around Danbury has only modest variations in elevation — a maximum elevation change of 663 ft around an average of 486 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,243 ft; within 50 miles, large variations in elevation — a maximum elevation change of 2,822 ft.

The land around Danbury is covered by trees (62%) and artificial surfaces (26%) within 2 miles, trees (83%) within 10 miles, and trees (72%) within 50 miles.

2 miles
663 ft
10 miles
1,243 ft
50 miles
2,822 ft
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Wilton 14 mi · Southbury 14 mi · Trumbull 17 mi · New Canaan 17 mi · Westport 18 mi · North Stamford 18 mi · Norwalk 19 mi · Shelton 19 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 Danbury (41.3948°, -73.454°, elevation 397 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).