Twin Falls weather in September

In September, Twin Falls sees average daytime highs of 78°F and overnight lows near 50°F, with 0.6 in of rain across 2.8 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 84°F in the first days to 73°F by the end. The sky is clear or mostly clear about 63% 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 Twin Falls's 3rd-clearest and 11th-windiest month. For the whole year in context, see Twin Falls's year-round climate.

Daytime high
78°
4th warmest
Overnight low
50°
9th coldest
Rainfall
0.6 in
2.8 wet days
Daylight
12 h 18 min
6:24 AM – 6:41 PM
Cloud cover
32%
3rd clearest
Wind
6 mph
11th windiest
Solar energy
5.56 kWh/m²
Travel score
8.1
out of 10

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

Density
1,009/km²
people per km²
Founded
1904

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 73°F by the end.

A typical September day in Twin Falls reaches about 78°F in the afternoon and slips back to 50°F overnight — a 28°F spread between the day's warmth and the night's chill. On most days the high lands between 65°F and 90°F. Set against its neighbours, September runs about 11°F cooler than August and about 14°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18555
28455
38455
48354
58354
68253
78253
88253
98152
108152
118051
128051
137951
147950
157850
167850
177849
187749
197749
207649
217648
227648
237548
247547
257547
267447
277446
287346
297346
307246

How September really feels in Twin 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.

Twin 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
Jan39° / 24°1.596.29.20.0
Feb44° / 27°1.17.44.210.30.8
Mar54° / 33°1.48.82.711.63.3
Apr61° / 38°1.48.21.413.15.3
May71° / 46°1.57.50.114.47.0
Jun81° / 53°0.84.2015.17.3
Jul91° / 60°0.21.7014.84.6
Aug89° / 59°0.31.9013.75.2
Sep78° / 50°0.62.8012.38.1
Oct64° / 40°0.94.60.410.86.6
Nov49° / 30°1.26.82.99.62.2
Dec38° / 24°1.68.86.28.90.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 63% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 14% of September, with mostly cloudy or overcast conditions the remaining 23%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
18218
28119
38020
48020
58020
67921
77921
87921
97822
107822
117624
127624
137624
147525
157525
167525
177525
187426
197525
207525
217624
227624
237624
247723
257723
267723
277723
287723
297723
307624

Chance of precipitation in September

Any precipitation

Twin Falls gets around 0.6 in of rain over 2.8 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 9% and peaks near 12% on the wettest days.

0%10%20%30%151015202530
Rain chance (%)
17
28
38
48
59
69
79
89
99
109
119
129
139
149
159
169
179
189
198
208
218
229
239
249
2510
2610
2711
2811
2912
3012

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 99% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)
1991
2991
3991
4982
5982
6982
7982
8982
9982
10991
11991
12991
13991
14991
15991
16991
17991
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 7 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
287calm
297calm
307calm

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 6:07 AM to 6:39 AM, and sunset from 7:08 PM to 6:15 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.06:077:08
213.06:087:06
312.96:097:04
412.96:107:03
512.86:127:01
612.86:136:59
712.76:146:57
812.76:156:55
912.66:166:54
1012.66:176:52
1112.56:186:50
1212.56:196:48
1312.46:206:46
1412.46:216:44
1512.36:236:43
1612.36:246:41
1712.26:256:39
1812.26:266:37
1912.16:276:35
2012.16:286:33
2112.06:296:31
2212.06:306:30
2311.96:316:28
2411.96:336:26
2511.86:346:24
2611.86:356:22
2711.76:366:20
2811.76:376:19
2911.66:386:17
3011.66:396:15

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.56 kWh/m².

For context, solar energy here swings from a low near 1.85 kWh/m² to a high of 7.98 kWh/m² in July across the year — September's 5.56 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.4Intense
26.3Intense
36.3Intense
46.2Intense
56.2Intense
66.1Intense
76.0Intense
86.0Bright
95.9Bright
105.9Bright
115.8Bright
125.8Bright
135.7Bright
145.6Bright
155.6Bright
165.5Bright
175.5Bright
185.4Bright
195.3Bright
205.3Bright
215.2Bright
225.2Bright
235.1Bright
245.1Bright
255.0Bright
265.0Bright
274.9Bright
284.8Bright
294.8Bright
304.7Bright
Planning a trip in September

Is September a good time to visit Twin Falls?

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

8.1
Sightseeing
1st-best month of the year
7.6
Beach & pool
4th-best month of the year

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

What to pack for Twin Falls in September

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

In September, Twin Falls sees daytime highs around 78°F and nights near 50°F. Worth packing: light clothes and sun protection.

light clothessun protection

UV index in Twin 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 Twin Falls peaks around June 19 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 13 at about 2 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJun 19UV 9Dec 13UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar4Moderate
Apr5Moderate
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov2Low
Dec2Low

Air quality in Twin 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 Twin Falls is worst in August — around 19 µg/m³ PM2.5 (moderate), about 3.3× the cleanest month (December, 6 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodAug 1918 µg/m³Dec 186 µg/m³
PM2.5 (µg/m³)Level
Jan7Good
Feb8Good
Mar10Good
Apr9Good
May9Good
Jun8Good
Jul16Moderate
Aug19Moderate
Sep17Moderate
Oct8Good
Nov7Good
Dec6Good
Location & terrain

Where is Twin Falls?

Twin Falls sits at 42.6°N, 114.5°W, 3,734 ft above sea level, in United States. The nearest listed city is Pocatello, 104 mi away.

Topography around Twin Falls

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

Within 2 miles, the terrain around Twin Falls has only modest variations in elevation — a maximum elevation change of 220 ft around an average of 3,727 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,634 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 7,808 ft.

The land around Twin Falls is covered by artificial surfaces (52%) within 2 miles, cropland (57%) and grassland (30%) within 10 miles, and grassland (73%) and cropland (22%) within 50 miles.

2 miles
220 ft
10 miles
1,634 ft
50 miles
7,808 ft
treesshrubsgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Pocatello 104 mi · Boise 114 mi · Kuna 118 mi · Meridian 121 mi · Eagle 124 mi · Nampa 126 mi · Caldwell 135 mi · Elko 137 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 Twin Falls (42.563°, -114.4609°, elevation 3,734 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).