Brighton weather in September

In September, Brighton sees average daytime highs of 79°F and overnight lows near 51°F, with 1.0 in of precipitation across 4.2 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 8th-wettest month of the year here.

Highs ease over the month, from about 84°F in the first days to 74°F by the end. The sky is clear or mostly clear about 56% 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 Brighton's 1st-clearest and 10th-windiest month. For the whole year in context, see Brighton's year-round climate.

Daytime high
79°
4th warmest
Overnight low
51°
9th coldest
Precipitation
1.0 in
4.2 wet days
Daylight
12 h 18 min
5:46 AM – 6:01 PM
Cloud cover
38%
1st clearest
Wind
5 mph
10th windiest
Solar energy
5.44 kWh/m²
Travel score
7.7
out of 10

Brighton is city in and county seat of Adams County, Colorado, United States.

Density
716/km²
people per km²
Founded
1887

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 84°F in the first days to 74°F by the end.

A typical September day in Brighton reaches about 79°F in the afternoon and slips back to 51°F overnight — a 27°F spread between the day's warmth and the night's chill. On most days the high lands between 66°F and 89°F. Set against its neighbours, September runs about 8°F cooler than August and about 13°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18457
28457
38456
48356
58356
68355
78255
88255
98154
108154
118053
128053
138052
147952
157952
167851
177851
187850
197750
207749
217649
227649
237648
247548
257547
267447
277447
287446
297346
307346

How September really feels in Brighton

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.

Brighton weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan42° / 19°0.53.33.59.50.4
Feb46° / 22°0.53.63.510.41.5
Mar56° / 29°1.35.43.411.74.3
Apr63° / 37°2.07.63.2135.8
May72° / 46°2.59.50.614.26.7
Jun83° / 55°1.57014.86.3
Jul89° / 61°1.36.9014.54.6
Aug87° / 60°1.25.7013.65.5
Sep79° / 51°1.04.20.412.37.7
Oct65° / 38°1.25.11.510.96.9
Nov52° / 27°0.74.13.39.83.4
Dec42° / 20°0.533.29.20.5

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 56% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 19% of September, with mostly cloudy or overcast conditions the remaining 25%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17624
27624
37624
47624
57624
67624
77624
87624
97624
107624
117624
127723
137624
147624
157624
167723
177624
187624
197624
207624
217624
227525
237525
247525
257426
267327
277327
287327
297228
307228

Chance of precipitation in September

Any precipitationSnow

Brighton gets around 1.0 in of rain and snow over 4.2 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 15% and peaks near 17% on the wettest days, and about 0 day brings snow.

0%10%20%30%151015202530
Rain chance (%)Snow chance (%)
1130
2140
3140
4140
5141
6141
7151
8151
9151
10161
11161
12161
13171
14171
15171
16171
17161
18161
19162
20152
21152
22152
23152
24152
25152
26152
27152
28152
29152
30152

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 98% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
19460
29550
39550
49541
59541
69631
79631
89631
99631
109721
119721
129721
139721
149811
159811
169811
179811
189910
199910
2010000
2110000
2210000
2310000
2410000
2510000
2610000
2710000
2810000
2910000
3010000

Wind in September

Winds average 5 mph in September.

Across September, daily wind ranges from about 5 mph on the calmest days to 5 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
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm

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 5:31 AM to 6:00 AM, and sunset from 6:27 PM to 5:37 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:316:27
212.95:326:25
312.85:336:23
412.85:346:22
512.75:356:20
612.75:366:18
712.75:376:17
812.65:386:15
912.65:396:13
1012.55:406:12
1112.55:416:10
1212.45:426:08
1312.45:436:07
1412.35:446:05
1512.35:456:03
1612.35:466:01
1712.25:476:00
1812.25:485:58
1912.15:495:56
2012.15:505:54
2112.05:515:53
2212.05:525:51
2311.95:535:49
2411.95:545:48
2511.95:555:46
2611.85:565:44
2711.85:575:43
2811.75:585:41
2911.75:595:39
3011.66:005:37

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.44 kWh/m².

For context, solar energy here swings from a low near 2.42 kWh/m² to a high of 7.39 kWh/m² in June across the year — September's 5.44 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.1Intense
26.0Intense
36.0Bright
46.0Bright
55.9Bright
65.9Bright
75.8Bright
85.8Bright
95.7Bright
105.7Bright
115.6Bright
125.6Bright
135.5Bright
145.5Bright
155.4Bright
165.4Bright
175.3Bright
185.3Bright
195.3Bright
205.2Bright
215.2Bright
225.1Bright
235.1Bright
245.0Bright
255.0Bright
264.9Bright
274.9Bright
284.8Bright
294.8Bright
304.7Bright
Planning a trip in September

Is September a good time to visit Brighton?

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

7.7
Sightseeing
1st-best month of the year
7.3
Beach & pool
2nd-best month of the year

September is one of the better times to visit Brighton for general sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Brighton in September

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

In September, Brighton sees daytime highs around 79°F and nights near 51°F. Worth packing: light clothes and sun protection. About 4 days see rain.

light clothessun protection

UV index in Brighton in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Brighton peaks around July 12 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highHighModerateJul 12UV 11Dec 23UV 2
UV index (midday)Level
Jan2Low
Feb4Moderate
Mar7High
Apr6High
May7Very high
Jun10Extreme
Jul11Extreme
Aug10Very high
Sep7Very high
Oct5High
Nov3Moderate
Dec2Low

Air quality in Brighton 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 Brighton is worst in August — around 21 µg/m³ PM2.5 (moderate), about 1.6× the cleanest month (May, 13 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateAug 1620 µg/m³May 1113 µg/m³
PM2.5 (µg/m³)Level
Jan17Moderate
Feb15Moderate
Mar16Moderate
Apr13Moderate
May13Moderate
Jun14Moderate
Jul14Moderate
Aug21Moderate
Sep13Moderate
Oct15Moderate
Nov15Moderate
Dec16Moderate
Location & terrain

Where is Brighton?

Brighton sits at 40.0°N, 104.8°W, 4,984 ft above sea level, in United States. The nearest listed city is Northglenn, 11 mi away.

Topography around Brighton

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

Within 2 miles, the terrain around Brighton has only modest variations in elevation — a maximum elevation change of 194 ft around an average of 4,990 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 640 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 9,626 ft.

The land around Brighton is covered by artificial surfaces (34%), grassland (32%) and cropland (21%) within 2 miles, grassland (51%) and cropland (28%) within 10 miles, and grassland (48%), trees (22%) and cropland (20%) within 50 miles.

2 miles
194 ft
10 miles
640 ft
50 miles
9,626 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Northglenn 11 mi · Thornton 11 mi · Erie 13 mi · Commerce City 14 mi · Sherrelwood 14 mi · Lafayette 14 mi · Broomfield 15 mi · Westminster 16 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 Brighton (39.9853°, -104.8205°, elevation 4,984 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. 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).