Guilford weather in September

In September, Guilford sees average daytime highs of 71°F and overnight lows near 63°F, with 4.1 in of rain across 8.7 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 5th-wettest month of the year here.

Highs ease over the month, from about 74°F in the first days to 68°F by the end. The sky is clear or mostly clear about 41% 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 Guilford's 2nd-clearest and 8th-windiest month. For the whole year in context, see Guilford's year-round climate.

Daytime high
71°
3rd warmest
Overnight low
63°
10th coldest
Rainfall
4.1 in
8.7 wet days
Daylight
12 h 18 min
5:37 AM – 5:53 PM
Cloud cover
53%
2nd clearest
Wind
10 mph
8th windiest
Solar energy
4.36 kWh/m²
Travel score
6.9
out of 10

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

Founded
1639

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 74°F in the first days to 68°F by the end.

A typical September day in Guilford reaches about 71°F in the afternoon and slips back to 63°F overnight — a 9°F spread between the day's warmth and the night's chill. On most days the high lands between 65°F and 77°F. Set against its neighbours, September runs about 5°F cooler than August and about 10°F warmer than October.

50°60°70°80°151015202530
Avg high (°F)Avg low (°F)
17566
27566
37466
47466
57465
67465
77465
87365
97365
107364
117364
127264
137264
147263
157263
167163
177162
187162
197062
207062
217061
227061
236961
246960
256960
266860
276859
286859
296759
306758

How September really feels in Guilford

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.

Guilford weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan37° / 28°3.99.94.69.40.0
Feb38° / 28°3.58.94.210.30.0
Mar43° / 34°4.810.53.311.70.5
Apr52° / 43°4.211.10.513.12.7
May61° / 52°3.510.9014.35.0
Jun71° / 62°3.79.8014.96.6
Jul77° / 69°3.19014.77.0
Aug77° / 68°3.99.2013.77.1
Sep71° / 63°4.18.7012.36.9
Oct62° / 53°4.89.70.110.95.3
Nov52° / 43°4.09.30.59.72.7
Dec43° / 34°5.110.939.10.5

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 41% 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 44%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15743
25743
35743
45644
55743
65743
75644
85743
95743
105743
115743
125743
135743
145743
155644
165644
175545
185644
195545
205446
215446
225446
235446
245446
255446
265347
275446
285446
295446
305545

Chance of precipitation in September

Any precipitation

Guilford gets around 4.1 in of rain over 8.7 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 32% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%40%151015202530
Rain chance (%)
125
225
325
425
526
626
726
826
927
1027
1127
1227
1327
1427
1528
1628
1728
1829
1929
2029
2130
2230
2330
2431
2531
2631
2731
2832
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 33% of days. Sticky, muggy-or-worse air turns up on roughly 23% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
11422272610
21523272510
31623262510
4182326249
5192325249
6202325239
7212325238
8232324238
9242324227
10252324227
11272223216
12282223215
13302223215
14312222204
15332222204
16342222193
17352222183
18362222182
19372222172
20392221172
21402221161
22412220161
23422220151
24432219141
25452219131
26462219131
27472218120
28492218110
29502217110
30512217100

Wind in September

Winds average 10 mph in September.

Across September, daily wind ranges from about 9 mph on the calmest days to 11 mph at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (mph)Feels
19light breeze
29light breeze
39light breeze
49light breeze
59light breeze
610light breeze
710light breeze
810light breeze
910light breeze
1010light breeze
1110light breeze
1210light breeze
1310light breeze
1410light breeze
1510light breeze
1610light breeze
1710light breeze
1810light breeze
1910light breeze
2010light breeze
2110light breeze
2210light breeze
2310light breeze
2410light breeze
2511light breeze
2611light breeze
2711light breeze
2811light breeze
2911light breeze
3011light breeze

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 5:21 AM to 5:52 AM, and sunset from 6:20 PM to 5:28 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:216:20
212.95:226:18
312.95:236:16
412.85:246:14
512.85:266:13
612.75:276:11
712.75:286:09
812.65:296:07
912.65:306:06
1012.65:316:04
1112.55:326:02
1212.55:336:00
1312.45:345:59
1412.45:355:57
1512.35:365:55
1612.35:375:53
1712.25:385:51
1812.25:395:50
1912.15:405:48
2012.15:415:46
2112.05:425:44
2212.05:435:42
2311.95:445:41
2411.95:455:39
2511.85:465:37
2611.85:475:35
2711.85:485:34
2811.75:505:32
2911.75:515:30
3011.65:525:28

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.36 kWh/m².

For context, solar energy here swings from a low near 1.72 kWh/m² to a high of 6.26 kWh/m² in June across the year — September's 4.36 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
15.0Bright
25.0Bright
34.9Bright
44.9Bright
54.8Bright
64.8Bright
74.7Bright
84.7Bright
94.7Bright
104.6Bright
114.6Bright
124.5Bright
134.5Bright
144.5Bright
154.4Bright
164.4Bright
174.3Bright
184.3Bright
194.3Bright
204.2Bright
214.2Bright
224.1Bright
234.1Bright
244.0Bright
254.0Moderate
263.9Moderate
273.9Moderate
283.8Moderate
293.8Moderate
303.7Moderate
Planning a trip in September

Hazard calendar for Guilford

In seasonPeak

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

Guilford 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 Guilford?

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

6.9
Sightseeing
3rd-best month of the year
4.7
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Guilford for sightseeing.

What to pack for Guilford in September

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

In September, Guilford sees daytime highs around 71°F and nights near 63°F. Worth packing: rain gear. About 9 days see rain.

rain gear

Sea temperature near Guilford in September

The nearest coast averages about 70°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 12 mi away) is warmest in August at about 72°F and coldest in February near 36°F.

It's comfortable for a long swim from Jul 8 to Sep 25 — about 2.6 months when the water holds above 68°F.

30°40°50°60°70°80°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°F)Comfort
Jan40Bracing
Feb36Bracing
Mar38Bracing
Apr44Bracing
May53Bracing
Jun63Cool
Jul70Refreshing
Aug72Refreshing
Sep70Refreshing
Oct64Cool
Nov55Bracing
Dec47Bracing

UV index in Guilford 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 Guilford 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 22 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJul 11UV 8Dec 22UV 1
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May7Very high
Jun8Very high
Jul8Very high
Aug6High
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low

Air quality in Guilford 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 Guilford is worst in July — around 20 µg/m³ PM2.5 (moderate), about 2.7× the cleanest month (November, 8 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1120 µg/m³Nov 188 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb13Moderate
Mar14Moderate
Apr16Moderate
May19Moderate
Jun20Moderate
Jul20Moderate
Aug17Moderate
Sep13Moderate
Oct9Good
Nov8Good
Dec9Good
Location & terrain

Where is Guilford?

Guilford sits at 41.3°N, 72.7°W, 46 ft above sea level, in United States. The nearest listed city is Madison, 4.3 mi away.

Topography around Guilford

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

Within 2 miles, the terrain around Guilford has only modest variations in elevation — a maximum elevation change of 233 ft around an average of 69 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 764 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,680 ft.

The land around Guilford is covered by trees (69%) within 2 miles, trees (52%) and water (40%) within 10 miles, and trees (56%) and water (36%) within 50 miles.

2 miles
233 ft
10 miles
764 ft
50 miles
1,680 ft
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Madison 4.3 mi · Branford 6.8 mi · East Haven 9.9 mi · North Haven 12 mi · New Haven 13 mi · Wallingford Center 13 mi · Hamden 14 mi · Wallingford 14 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 Guilford (41.289°, -72.6818°, elevation 46 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).