Merrifield weather in September

In September, Merrifield sees average daytime highs of 79°F and overnight lows near 62°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 1st-wettest month of the year here.

Highs ease over the month, from about 83°F in the first days to 74°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 Merrifield's 3rd-clearest and 9th-windiest month. For the whole year in context, see Merrifield's year-round climate.

Daytime high
79°
4th warmest
Overnight low
62°
9th coldest
Rainfall
4.3 in
9.4 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
4.29 kWh/m²
Travel score
6.8
out of 10

Merrifield is census designated place in Fairfax County, Virginia, United States.

Density
2,173/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 74°F by the end.

A typical September day in Merrifield reaches about 79°F in the afternoon and slips back to 62°F overnight — a 17°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)
18367
28367
38367
48366
58266
68266
78265
88265
98165
108164
118064
128064
138063
147963
157962
167962
177862
187861
197861
207761
217760
227660
237660
247659
257559
267558
277558
287458
297457
307457

How September really feels in Merrifield

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.

Merrifield 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
Jan43° / 29°3.18.72.89.60.6
Feb46° / 31°2.88.52.510.51.4
Mar55° / 38°3.910.31.711.73.5
Apr66° / 48°3.49.90136.0
May75° / 57°3.711.4014.16.5
Jun84° / 66°3.511.4014.75.4
Jul88° / 71°3.811.7014.44.3
Aug86° / 69°3.510.1013.55.1
Sep79° / 62°4.39.4012.36.8
Oct67° / 51°3.47.90116.6
Nov56° / 40°2.97.60.29.94.2
Dec47° / 33°3.48.91.69.31.6

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 48%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15248
25248
35248
45347
55347
65347
75347
85347
95347
105347
115347
125248
135248
145248
155248
165149
175050
185050
195050
205050
215050
224951
235050
245050
255149
265248
275248
285347
295446
305446

Chance of precipitation in September

Any precipitation

Merrifield gets around 4.3 in of rain over 9.4 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 29% and peaks near 31% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
130
231
331
431
531
631
731
831
931
1030
1130
1230
1329
1429
1529
1628
1728
1829
1929
2029
2129
2229
2329
2429
2529
2628
2728
2828
2927
3027

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 30% of days. Sticky, muggy-or-worse air turns up on roughly 28% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
112182527181
213182426181
314182426171
415182425171
517192424161
618192424151
719192423141
820202423131
921202422121
1022202422110
1123202522100
122420252190
132620252180
142720242170
152820242170
162920242060
173120242050
183220241950
193320231940
203520231940
213620221830
223820221830
233920211820
244120201720
254219201720
264419191620
274619191520
284718181520
294918181420
305117171320

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
95calm
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 5:42 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)
112.95:426:35
212.85:436:34
312.85:446:32
412.85:456:30
512.75:466:29
612.75:476:27
712.65:476:26
812.65:486:24
912.65:496:22
1012.55:506:21
1112.55:516:19
1212.45:526:17
1312.45:536:16
1412.35:546:14
1512.35:556:12
1612.25:566:11
1712.25:576:09
1812.25:586:07
1912.15:596:06
2012.15:596:04
2112.06:006:02
2212.06:016:01
2311.96:025:59
2411.96:035:57
2511.96:045:56
2611.86:055:54
2711.86:065:52
2811.76:075:51
2911.76:085:49
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 4.29 kWh/m².

For context, solar energy here swings from a low near 1.98 kWh/m² to a high of 6.15 kWh/m² in June across the year — September's 4.29 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.8Bright
24.8Bright
34.8Bright
44.7Bright
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
244.0Moderate
254.0Moderate
263.9Moderate
273.9Moderate
283.9Moderate
293.8Moderate
303.8Moderate
Planning a trip in September

Hazard calendar for Merrifield

In seasonPeak

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

Merrifield 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 Merrifield?

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

6.8
Sightseeing
1st-best month of the year
6.5
Beach & pool
3rd-best month of the year

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

What to pack for Merrifield in September

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

In September, Merrifield sees daytime highs around 79°F and nights near 62°F. Worth packing: light clothes and rain gear. About 9 days see rain.

light clothesrain gear

UV index in Merrifield 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 Merrifield 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 Merrifield 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 Merrifield is worst in July — around 17 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (November, 9 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1317 µg/m³Nov 129 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb12Moderate
Mar13Moderate
Apr13Moderate
May15Moderate
Jun16Moderate
Jul17Moderate
Aug15Moderate
Sep12Moderate
Oct9Good
Nov9Good
Dec10Good
Location & terrain

Where is Merrifield?

Merrifield sits at 38.9°N, 77.2°W, 361 ft above sea level, in United States. The nearest listed city is Idylwood, 1.9 mi away.

Topography around Merrifield

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

Within 2 miles, the terrain around Merrifield has only modest variations in elevation — a maximum elevation change of 246 ft around an average of 364 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 574 ft; within 50 miles, large variations in elevation — a maximum elevation change of 2,533 ft.

The land around Merrifield is covered by trees (69%) and artificial surfaces (24%) within 2 miles, trees (77%) within 10 miles, and trees (62%) within 50 miles.

2 miles
246 ft
10 miles
574 ft
50 miles
2,533 ft
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Idylwood 1.9 mi · West Falls Church 2.5 mi · Vienna 2.5 mi · Tysons 3.1 mi · Annandale 3.7 mi · Oakton 3.7 mi · Fairfax 5.0 mi · McLean 5.0 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 Merrifield (38.8743°, -77.2269°, elevation 361 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).