Bozeman weather in September

In September, Bozeman sees average daytime highs of 66°F and overnight lows near 40°F, with 2.1 in of precipitation across 8.3 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 5th-wettest month of the year here.

Highs ease over the month, from about 72°F in the first days to 61°F by the end. The sky is clear or mostly clear about 45% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 06 min at the start of September to 11 h 30 min by month's end. Set against the rest of the year, September is Bozeman's 3rd-clearest and 10th-windiest month. For the whole year in context, see Bozeman's year-round climate.

Daytime high
66°
4th warmest
Overnight low
40°
9th coldest
Precipitation
2.1 in
8.3 wet days
Daylight
12 h 18 min
6:09 AM – 6:28 PM
Cloud cover
45%
3rd clearest
Wind
4 mph
10th windiest
Solar energy
4.91 kWh/m²
Travel score
6.4
out of 10

Bozeman is city and the county seat of Gallatin County, Montana, United States.

Density
875/km²
people per km²
Founded
1864

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 72°F in the first days to 61°F by the end.

A typical September day in Bozeman reaches about 66°F in the afternoon and slips back to 40°F overnight — a 26°F spread between the day's warmth and the night's chill. On most days the high lands between 52°F and 79°F. Set against its neighbours, September runs about 11°F cooler than August and about 15°F warmer than October.

20°40°60°80°151015202530
Avg high (°F)Avg low (°F)
17344
27344
37244
47243
57143
67143
77042
87042
96942
106941
116841
126841
136740
146740
156640
166640
176539
186539
196439
206438
216438
226338
236338
246337
256237
266237
276136
286136
296036
306035

How September really feels in Bozeman

Once humidity and wind are folded in, September averages 0 days that feel above 90°F and 2 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
2
wind chill below the day's low

The story in September is cold — wind chill drags the overnight "feels like" below the raw low.

Bozeman weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan28° / 12°1.28.798.90.0
Feb31° / 13°1.38.69.310.10.0
Mar39° / 19°1.911.39.511.60.1
Apr47° / 26°3.214.19.513.31.4
May58° / 35°4.016.33.214.73.6
Jun67° / 42°4.214.40.715.45.6
Jul78° / 48°2.08.6015.17.3
Aug77° / 47°1.67.2013.97.6
Sep66° / 40°2.18.30.912.36.4
Oct51° / 29°2.310.64.810.72.6
Nov37° / 17°1.79.58.49.30.0
Dec28° / 10°1.38.798.60.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 45% 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 37%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16931
26931
36832
46832
56733
66634
76634
86535
96436
106337
116337
126238
136238
146139
156139
166139
176139
186139
196139
206139
216139
226337
236337
246337
256337
266238
276238
286238
296238
306238

Chance of precipitation in September

Any precipitationSnow

Bozeman gets around 2.1 in of rain and snow over 8.3 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 28% and peaks near 31% on the wettest days, and about 1 day brings snow.

0%10%20%30%40%151015202530
Rain chance (%)Snow chance (%)
1240
2240
3251
4251
5261
6271
7271
8282
9292
10302
11302
12313
13313
14313
15313
16314
17314
18304
19304
20294
21294
22285
23285
24285
25286
26286
27287
28287
29288
30289

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 100% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)
1991
2991
31000
41000
51000
61000
71000
81000
91000
101000
111000
121000
131000
141000
151000
161000
171000
181000
191000
201000
211000
221000
231000
241000
251000
261000
271000
281000
291000
301000

Wind in September

Winds average 4 mph in September.

Across September, daily wind ranges from about 4 mph on the calmest days to 4 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
14calm
24calm
34calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 06 min at the start of September to 11 h 30 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 96 minutes over September. Sunrise moves from 5:50 AM to 6:27 AM, and sunset from 6:58 PM to 6:00 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.15:506:58
213.15:516:56
313.05:526:54
413.05:546:52
512.95:556:50
612.95:566:48
712.85:586:46
812.85:596:44
912.76:006:42
1012.66:016:40
1112.66:036:38
1212.56:046:36
1312.56:056:34
1412.46:066:32
1512.46:086:30
1612.36:096:28
1712.36:106:26
1812.26:126:24
1912.26:136:22
2012.16:146:20
2112.06:156:18
2212.06:176:16
2311.96:186:14
2411.96:196:12
2511.86:216:10
2611.86:226:08
2711.76:236:06
2811.76:246:04
2911.66:266:02
3011.56:276:00

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.91 kWh/m².

For context, solar energy here swings from a low near 1.67 kWh/m² to a high of 7.6 kWh/m² in July across the year — September's 4.91 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.8Bright
25.7Bright
35.7Bright
45.6Bright
55.5Bright
65.5Bright
75.4Bright
85.3Bright
95.3Bright
105.2Bright
115.1Bright
125.1Bright
135.0Bright
145.0Bright
154.9Bright
164.8Bright
174.8Bright
184.7Bright
194.7Bright
204.6Bright
214.6Bright
224.5Bright
234.5Bright
244.4Bright
254.4Bright
264.3Bright
274.3Bright
284.2Bright
294.2Bright
304.1Bright
Planning a trip in September

Hazard calendar for Bozeman

In seasonPeak

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

Bozeman's rainy season runs March–July, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Bozeman?

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

6.4
Sightseeing
3rd-best month of the year
2.9
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Bozeman for sightseeing.

What to pack for Bozeman in September

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

In September, Bozeman sees daytime highs around 66°F and nights near 40°F. Worth packing: a warm layer, rain gear and sun protection. About 8 days see rain.

a warm layerrain gearsun protection

UV index in Bozeman 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 Bozeman peaks around July 12 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 at about 1 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateVery highHighModerateLowJul 12UV 9Jan 1UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar4Moderate
Apr5Moderate
May7Very high
Jun9Very high
Jul9Very high
Aug7Very high
Sep6High
Oct4Moderate
Nov2Low
Dec1Low

Air quality in Bozeman 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 Bozeman is worst in August — around 19 µg/m³ PM2.5 (moderate), about 3.2× the cleanest month (January, 6 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodAug 1618 µg/m³Jan 126 µg/m³
PM2.5 (µg/m³)Level
Jan6Good
Feb7Good
Mar9Good
Apr10Good
May10Good
Jun9Good
Jul15Moderate
Aug19Moderate
Sep15Moderate
Oct7Good
Nov8Good
Dec6Good
Location & terrain

Where is Bozeman?

Bozeman sits at 45.7°N, 111.0°W, 4,816 ft above sea level, in United States. The nearest listed city is Butte, 75 mi away.

Topography around Bozeman

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

Within 2 miles, the terrain around Bozeman has only modest variations in elevation — a maximum elevation change of 627 ft around an average of 4,843 ft above sea level; within 10 miles, very significant variations in elevation — a maximum elevation change of 4,731 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 7,293 ft.

The land around Bozeman is covered by artificial surfaces (36%), grassland (32%) and trees (23%) within 2 miles, grassland (44%) and trees (34%) within 10 miles, and grassland (54%) and trees (36%) within 50 miles.

2 miles
627 ft
10 miles
4,731 ft
50 miles
7,293 ft
treesgrasslandcroplandartificial surfacesbare terrainmoss and lichen
September weather nearby: Butte 75 mi · Helena 79 mi · Billings 122 mi · Great Falls 126 mi · Rexburg 133 mi · Idaho Falls 160 mi · Missoula 163 mi · Conda 206 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 Bozeman (45.6797°, -111.0386°, elevation 4,816 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).