Hillsborough weather in September

In September, Hillsborough sees average daytime highs of 76°F and overnight lows near 59°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 4th-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 35% 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 Hillsborough's 2nd-clearest and 9th-windiest month. For the whole year in context, see Hillsborough's year-round climate.

Daytime high
76°
4th warmest
Overnight low
59°
9th coldest
Rainfall
4.1 in
9.2 wet days
Daylight
12 h 18 min
5:45 AM – 6:01 PM
Cloud cover
56%
2nd clearest
Wind
6 mph
9th windiest
Solar energy
4.19 kWh/m²
Travel score
6.9
out of 10

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 Hillsborough reaches about 76°F in the afternoon and slips back to 59°F overnight — a 17°F spread between the day's warmth and the night's chill. On most days the high lands between 67°F and 85°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)
18164
28163
38063
48063
58063
68062
77962
87962
97961
107861
117861
127860
137760
147760
157759
167659
177658
187658
197558
207557
217457
227456
237456
247356
257355
267355
277255
287254
297154
307154

How September really feels in Hillsborough

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.

Hillsborough 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
Jan39° / 25°3.39.14.39.40.0
Feb42° / 26°3.093.710.40.3
Mar50° / 33°4.210.63.311.72.2
Apr62° / 43°3.710.70.4135.0
May71° / 53°3.611.7014.26.3
Jun81° / 62°4.311.5014.86.0
Jul85° / 68°4.211.3014.65.0
Aug83° / 66°4.010.4013.65.8
Sep76° / 59°4.19.2012.36.9
Oct65° / 47°3.78.60.110.96.0
Nov53° / 38°3.07.90.59.73.2
Dec44° / 30°4.09.62.69.20.6

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 35% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 16% of September, with mostly cloudy or overcast conditions the remaining 50%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15149
25149
35050
45050
55149
65050
75050
85050
95149
105149
115149
125149
135149
145149
155149
165149
175050
185149
195050
205050
215050
225050
235050
245050
254951
264951
275050
285050
295149
305248

Chance of precipitation in September

Any precipitation

Hillsborough 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 29% and peaks near 31% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
127
227
328
428
528
629
729
829
929
1029
1130
1230
1329
1429
1529
1629
1730
1830
1930
2030
2131
2231
2331
2431
2530
2630
2730
2830
2930
3030

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 42% of days. Sticky, muggy-or-worse air turns up on roughly 18% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1262321219
2262321209
3272320209
4282320199
5292420189
6302420189
7312419178
8322419168
9332419168
10342419157
11352419157
12362319156
13382319146
14392320145
15402220135
16422220134
17432120124
18442120123
19462019123
20472019112
21491919112
22501918112
23511918111
24541817101
25551816101
26561716101
2758171591
2859161591
2960161491
3061161481

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 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 5:30 AM to 5:59 AM, and sunset from 6:26 PM to 5:36 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:306:26
212.95:316:25
312.95:326:23
412.85:336:21
512.85:346:20
612.75:356:18
712.75:366:16
812.65:376:15
912.65:386:13
1012.55:396:11
1112.55:406:09
1212.45:416:08
1312.45:426:06
1412.45:436:04
1512.35:446:02
1612.35:456:01
1712.25:465:59
1812.25:475:57
1912.15:485:56
2012.15:495:54
2112.05:505:52
2212.05:515:50
2311.95:525:49
2411.95:535:47
2511.95:545:45
2611.85:555:43
2711.85:565:42
2811.75:575:40
2911.75:585:38
3011.65:595:36

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.19 kWh/m².

For context, solar energy here swings from a low near 1.77 kWh/m² to a high of 5.99 kWh/m² in June across the year — September's 4.19 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.8Bright
24.7Bright
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
214.0Bright
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 Hillsborough

In seasonPeak

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

Hillsborough 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 Hillsborough?

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
6.0
Beach & pool
4th-best month of the year

September is a reasonable time to visit Hillsborough for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Hillsborough in September

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

In September, Hillsborough sees daytime highs around 76°F and nights near 59°F. Worth packing: light clothes and rain gear. About 9 days see rain.

light clothesrain gear

Sea temperature near Hillsborough 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 40 mi away) is warmest in August at about 74°F and coldest in February near 40°F.

It's comfortable for a long swim from Jun 30 to Sep 27 — about 3 months when the water holds above 68°F.

40°50°60°70°80°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°F)Comfort
Jan43Bracing
Feb40Bracing
Mar41Bracing
Apr46Bracing
May55Bracing
Jun65Cool
Jul72Refreshing
Aug74Refreshing
Sep71Refreshing
Oct64Cool
Nov55Bracing
Dec49Bracing

UV index in Hillsborough 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 Hillsborough peaks around July 11 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 1 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJul 11UV 8Dec 21UV 1
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun8Very high
Jul8Very high
Aug6High
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low

Air quality in Hillsborough 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 Hillsborough is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.0× the cleanest month (November, 9 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1518 µg/m³Nov 149 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb13Moderate
Mar14Moderate
Apr14Moderate
May16Moderate
Jun17Moderate
Jul18Moderate
Aug15Moderate
Sep13Moderate
Oct10Good
Nov9Good
Dec10Good
Location & terrain

Where is Hillsborough?

Hillsborough sits at 40.5°N, 74.6°W, 85 ft above sea level, in United States. The nearest listed city is Somerset, 7.5 mi away.

Topography around Hillsborough

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

Within 2 miles, the terrain around Hillsborough has only modest variations in elevation — a maximum elevation change of 161 ft around an average of 105 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 673 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,962 ft.

The land around Hillsborough is covered by trees (56%) and grassland (29%) within 2 miles, trees (64%) and grassland (22%) within 10 miles, and trees (61%) within 50 miles.

2 miles
161 ft
10 miles
673 ft
50 miles
1,962 ft
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Somerset 7.5 mi · North Brunswick 8.1 mi · Bridgewater 8.7 mi · Princeton 9.3 mi · New Brunswick 9.3 mi · Warren Township 11 mi · East Brunswick 12 mi · Edison 12 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 Hillsborough (40.4776°, -74.6268°, elevation 85 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).