Montclair weather in September

In September, Montclair sees average daytime highs of 79°F and overnight lows near 63°F, with 4.2 in of rain across 9.5 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 1st-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 36% of the time in September, and the air most often feels humid.

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 Montclair's 3rd-clearest and 9th-windiest month. For the whole year in context, see Montclair's year-round climate.

Daytime high
79°
4th warmest
Overnight low
63°
9th coldest
Rainfall
4.2 in
9.5 wet days
Daylight
12 h 12 min
5:56 AM – 6:11 PM
Cloud cover
56%
3rd clearest
Wind
6 mph
9th windiest
Solar energy
4.3 kWh/m²
Travel score
6.7
out of 10

Montclair is census designated place in Prince William County, Virginia, United States.

Density
1,224/km²
people per km²

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 Montclair reaches about 79°F in the afternoon and slips back to 63°F overnight — a 16°F spread between the day's warmth and the night's chill. On most days the high lands between 70°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)
18368
28368
38367
48367
58267
68267
78266
88266
98166
108165
118165
128065
138064
148064
157964
167963
177863
187862
197862
207762
217761
227761
237661
247660
257660
267560
277559
287559
297458
307458

How September really feels in Montclair

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.

Montclair weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 1st-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan44° / 30°3.18.52.79.60.9
Feb47° / 31°2.88.22.310.51.6
Mar56° / 39°3.910.21.611.73.8
Apr67° / 49°3.39.40136.2
May75° / 58°3.510.9014.16.6
Jun84° / 67°3.511.2014.65.5
Jul88° / 72°3.711.7014.44.3
Aug85° / 70°3.510.2013.55.1
Sep79° / 63°4.29.5012.36.7
Oct68° / 52°3.47.80116.7
Nov57° / 41°2.97.30.19.94.4
Dec48° / 34°3.48.81.49.41.9

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 36% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 18% of September, with mostly cloudy or overcast conditions the remaining 47%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15446
25446
35446
45446
55446
65545
75545
85644
95545
105545
115644
125545
135545
145545
155446
165347
175248
185248
195149
205149
215050
225149
235149
245149
255149
265347
275347
285347
295446
305545

Chance of precipitation in September

Any precipitation

Montclair gets around 4.2 in of rain over 9.5 wet days in September, the wettest month. 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 33% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
132
232
332
433
533
633
733
832
932
1031
1131
1230
1330
1429
1529
1629
1729
1829
1929
2029
2129
2229
2329
2429
2529
2628
2728
2828
2927
3027

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels humid — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the humid band about 25% of days. Sticky, muggy-or-worse air turns up on roughly 32% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
17152727231
28162727221
39162726211
49172725201
510172725191
611182724181
712182823171
813192823161
915202822151
1016202822141
1117202722131
1218212722121
1319212722110
1421212722100
152221272290
162321262180
172521262170
182621262160
192721252150
202821252150
213021242140
223221242030
233321232030
243520231930
253720221920
263820221820
274019211820
284219201720
294419201620
304518191520

Wind in September

Winds average 6 mph in September.

Across September, daily wind ranges from about 5 mph on the calmest days to 6 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
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 5:43 AM to 6:09 AM, and sunset from 6:35 PM to 5:48 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:436:35
212.85:446:34
312.85:446:32
412.85:456:31
512.75:466:29
612.75:476:28
712.65:486:26
812.65:496:24
912.55:506:23
1012.55:516:21
1112.55:526:19
1212.45:536:18
1312.45:546:16
1412.35:546:14
1512.35:556:13
1612.25:566:11
1712.25:576:09
1812.25:586:08
1912.15:596:06
2012.16:006:04
2112.06:016:03
2212.06:026:01
2311.96:035:59
2411.96:045:58
2511.96:055:56
2611.86:065:55
2711.86:065:53
2811.76:075:51
2911.76:085:50
3011.66:095:48

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.3 kWh/m².

For context, solar energy here swings from a low near 2.01 kWh/m² to a high of 6.15 kWh/m² in June across the year — September's 4.3 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.9Bright
24.8Bright
34.8Bright
44.8Bright
54.7Bright
64.7Bright
74.6Bright
84.6Bright
94.6Bright
104.5Bright
114.5Bright
124.5Bright
134.4Bright
144.4Bright
154.3Bright
164.3Bright
174.3Bright
184.2Bright
194.2Bright
204.1Bright
214.1Bright
224.1Bright
234.0Bright
244.0Bright
254.0Moderate
263.9Moderate
273.9Moderate
283.9Moderate
293.9Moderate
303.8Moderate
Planning a trip in September

Hazard calendar for Montclair

In seasonPeak

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

Montclair 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 Montclair?

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

6.7
Sightseeing
1st-best month of the year
6.5
Beach & pool
3rd-best month of the year

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

What to pack for Montclair in September

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

In September, Montclair sees daytime highs around 79°F and nights near 63°F. Worth packing: light clothes and rain gear. About 10 days see rain.

light clothesrain gear

UV index in Montclair 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 Montclair peaks around July 11 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 2 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJul 11UV 9Dec 19UV 2
UV index (midday)Level
Jan2Moderate
Feb3Moderate
Mar5High
Apr6High
May8Very high
Jun9Very high
Jul9Very high
Aug7High
Sep6High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Montclair 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 Montclair is worst in July — around 16 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (November, 7 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1416 µg/m³Nov 187 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb10Good
Mar12Good
Apr13Moderate
May14Moderate
Jun15Moderate
Jul16Moderate
Aug14Moderate
Sep11Good
Oct8Good
Nov7Good
Dec8Good
Location & terrain

Where is Montclair?

Montclair sits at 38.6°N, 77.3°W, 125 ft above sea level, in United States. The nearest listed city is Dale City, 2.5 mi away.

Topography around Montclair

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

Within 2 miles, the terrain around Montclair has only modest variations in elevation — a maximum elevation change of 302 ft around an average of 230 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 577 ft; within 50 miles, large variations in elevation — a maximum elevation change of 3,514 ft.

The land around Montclair is covered by trees (78%) within 2 miles, trees (74%) within 10 miles, and trees (69%) within 50 miles.

2 miles
302 ft
10 miles
577 ft
50 miles
3,514 ft
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Dale City 2.5 mi · Cherry Hill 5.0 mi · Lake Ridge 5.6 mi · Lorton 8.7 mi · Buckhall 9.9 mi · Manassas 12 mi · West Springfield 13 mi · Burke 13 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 Montclair (38.611°, -77.3397°, elevation 125 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). 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).