Idaho Falls weather in September

In September, Idaho Falls sees average daytime highs of 74°F and overnight lows near 47°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 10th-wettest month of the year here.

Highs ease over the month, from about 80°F in the first days to 68°F by the end. The sky is clear or mostly clear about 57% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Idaho Falls's 3rd-clearest and 9th-windiest month. For the whole year in context, see Idaho Falls's year-round climate.

Daytime high
74°
4th warmest
Overnight low
47°
9th coldest
Precipitation
1.0 in
4.2 wet days
Daylight
12 h 18 min
6:14 AM – 6:31 PM
Cloud cover
36%
3rd clearest
Wind
6 mph
9th windiest
Solar energy
5.36 kWh/m²
Travel score
8.0
out of 10

Idaho Falls is city in and county seat of Bonneville County, Idaho, United States.

Density
988/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 80°F in the first days to 68°F by the end.

A typical September day in Idaho Falls reaches about 74°F in the afternoon and slips back to 47°F overnight — a 27°F spread between the day's warmth and the night's chill. On most days the high lands between 61°F and 84°F. Set against its neighbours, September runs about 11°F cooler than August and about 15°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18052
28051
38051
47951
57950
67850
77850
87749
97749
107649
117648
127548
137547
147447
157447
167347
177346
187346
197246
207245
217145
227145
237144
247044
257044
266944
276943
286843
296842
306742

How September really feels in Idaho Falls

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.

Idaho Falls weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 10th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan31° / 17°1.49.410.39.10.0
Feb36° / 21°1.17.87.310.20.0
Mar47° / 29°1.49.24.611.61.6
Apr56° / 34°1.811.2313.23.7
May66° / 42°2.19.60.814.56.1
Jun76° / 50°1.260.115.27.5
Jul87° / 57°0.53.3014.95.9
Aug85° / 55°0.53.5013.86.5
Sep74° / 47°1.04.20.112.38.0
Oct58° / 36°1.36.51.210.85.0
Nov43° / 26°1.27.45.59.50.7
Dec31° / 18°1.59.49.78.80.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 57% 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 27%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17921
27921
37921
47723
57723
67723
77624
87624
97624
107525
117525
127525
137327
147327
157327
167129
177129
187129
197129
207030
217030
227030
237030
247030
256931
266832
276832
286832
296832
306733

Chance of precipitation in September

Any precipitationSnow

Idaho Falls 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 19% on the wettest days, and about 0 day brings snow.

0%10%20%30%151015202530
Rain chance (%)Snow chance (%)
1130
2130
3130
4130
5130
6130
7140
8140
9140
10140
11140
12140
13140
14140
15140
16140
17140
18140
19140
20140
21140
22140
23150
24151
25161
26161
27171
28181
29181
30192

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
3991
4991
5991
6991
7991
8991
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 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 13 hours 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 84 minutes over September. Sunrise moves from 5:56 AM to 6:30 AM, and sunset from 6:59 PM to 6:05 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:566:59
213.05:586:57
312.95:596:56
412.96:006:54
512.86:016:52
612.86:026:50
712.76:036:48
812.76:046:46
912.66:066:44
1012.66:076:43
1112.56:086:41
1212.56:096:39
1312.46:106:37
1412.46:116:35
1512.36:136:33
1612.36:146:31
1712.26:156:29
1812.26:166:27
1912.16:176:26
2012.16:186:24
2112.06:196:22
2212.06:216:20
2311.96:226:18
2411.96:236:16
2511.86:246:14
2611.86:256:12
2711.76:266:10
2811.76:286:09
2911.66:296:07
3011.66:306:05

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.36 kWh/m².

For context, solar energy here swings from a low near 1.7 kWh/m² to a high of 7.94 kWh/m² in July across the year — September's 5.36 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.2Intense
26.1Intense
36.1Intense
46.0Intense
56.0Bright
65.9Bright
75.8Bright
85.8Bright
95.7Bright
105.7Bright
115.6Bright
125.5Bright
135.5Bright
145.4Bright
155.4Bright
165.3Bright
175.3Bright
185.2Bright
195.1Bright
205.1Bright
215.0Bright
225.0Bright
234.9Bright
244.9Bright
254.8Bright
264.7Bright
274.7Bright
284.6Bright
294.5Bright
304.5Bright
Planning a trip in September

Is September a good time to visit Idaho Falls?

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

8.0
Sightseeing
1st-best month of the year
6.1
Beach & pool
4th-best month of the year

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

What to pack for Idaho Falls in September

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

In September, Idaho Falls sees daytime highs around 74°F and nights near 47°F. Worth packing: light clothes and sun protection. About 4 days see rain.

light clothessun protection

UV index in Idaho Falls 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 Idaho Falls 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 2 (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 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr5Moderate
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov2Low
Dec2Low

Air quality in Idaho Falls 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 Idaho Falls is worst in August — around 20 µg/m³ PM2.5 (moderate), about 3.1× the cleanest month (December, 7 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodAug 1420 µg/m³Dec 197 µg/m³
PM2.5 (µg/m³)Level
Jan8Good
Feb9Good
Mar10Good
Apr10Good
May10Good
Jun9Good
Jul17Moderate
Aug20Moderate
Sep14Moderate
Oct9Good
Nov9Good
Dec7Good
Location & terrain

Where is Idaho Falls?

Idaho Falls sits at 43.5°N, 112.0°W, 4,705 ft above sea level, in United States. The nearest listed city is Rexburg, 28 mi away.

Topography around Idaho Falls

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

Within 2 miles, the terrain around Idaho Falls has only modest variations in elevation — a maximum elevation change of 95 ft around an average of 4,698 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,693 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 5,561 ft.

The land around Idaho Falls is covered by artificial surfaces (33%) and trees (22%) within 2 miles, cropland (45%) and grassland (38%) within 10 miles, and grassland (54%) and cropland (22%) within 50 miles.

2 miles
95 ft
10 miles
1,693 ft
50 miles
5,561 ft
treesshrubsgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Rexburg 28 mi · Pocatello 46 mi · Conda 57 mi · Logan 120 mi · Brigham City 135 mi · Twin Falls 137 mi · North Ogden 149 mi · Ogden 155 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 Idaho Falls (43.4666°, -112.0341°, elevation 4,705 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).