Sun Valley weather in September

In September, Sun Valley sees average daytime highs of 77°F and overnight lows near 50°F, with 0.4 in of rain across 2.5 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 82°F in the first days to 72°F by the end. The sky is clear or mostly clear about 76% 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 Sun Valley's 2nd-clearest and 7th-windiest month. For the whole year in context, see Sun Valley's year-round climate.

Daytime high: 77°; 4th warmest
Overnight low: 50°; 10th coldest
Rainfall: 0.4 in; 2.5 wet days
Daylight: 12 h 18 min; 5:46 AM – 6:01 PM
Cloud cover: 22%; 2nd clearest
Wind: 4 mph; 7th windiest
Solar energy: 6.08 kWh/m²
Travel score: 8.6; out of 10

Sun Valley is place in Washoe County, Nevada, USA.

Density: 500/km²; people per km²

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

← August Sun Valley year-round climate October →Best places to visit in September

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

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 82°F in the first days to 72°F by the end.

A typical September day in Sun Valley reaches about 77°F in the afternoon and slips back to 50°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 86°F. Set against its neighbours, September runs about 8°F cooler than August and about 13°F warmer than October.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Avg high (°F)	82	82	82	81	81	81	80	80	80	79	79	78	78	78	77	77	76	76	76	76	75	75	74	74	74	73	73	73	72	72
Avg low (°F)	54	53	53	53	53	53	52	52	52	51	51	51	51	50	50	50	50	49	49	49	49	48	48	48	47	47	47	46	46	46

	Avg high (°F)	Avg low (°F)
1	82	54
2	82	53
3	82	53
4	81	53
5	81	53
6	81	53
7	80	52
8	80	52
9	80	52
10	79	51
11	79	51
12	78	51
13	78	51
14	78	50
15	77	50
16	77	50
17	76	50
18	76	49
19	76	49
20	76	49
21	75	49
22	75	48
23	74	48
24	74	48
25	74	47
26	73	47
27	73	47
28	73	46
29	72	46
30	72	46

How September really feels in Sun Valley

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

heat index over the day's high

Days feeling ≤ 32°F

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.

Sun Valley 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.

Month	High / Low (°F)	Rainfall (inches)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	40° / 22°	2.6	8	6.8	9.5	0.0
Feb	43° / 24°	2.3	8.5	7.3	10.4	0.6
Mar	50° / 28°	2.2	8	6	11.7	2.4
Apr	57° / 34°	1.3	6.9	3.6	13	4.4
May	67° / 42°	1.2	6.8	1.2	14.1	6.8
Jun	78° / 50°	0.6	3.5	0.2	14.7	8.1
Jul	87° / 56°	0.4	2.8	0	14.5	6.1
Aug	85° / 56°	0.3	2.7	0	13.6	6.6
Sep	77° / 50°	0.4	2.5	0	12.3	8.6
Oct	64° / 40°	0.9	3.5	0.8	10.9	7.0
Nov	50° / 29°	1.4	5.7	3.6	9.8	2.6
Dec	39° / 21°	2.5	7.6	6.6	9.3	0.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 76% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 12% of September, with mostly cloudy or overcast conditions the remaining 12%. Skies tend to cloud over as the month goes on.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Clearer (%)	92	92	91	91	91	91	91	91	90	90	90	90	89	88	88	88	88	88	88	88	87	87	87	87	87	86	86	84	84	84
Cloudier (%)	8	8	9	9	9	9	9	9	10	10	10	10	11	12	12	12	12	12	12	12	13	13	13	13	13	14	14	16	16	16

	Clearer (%)	Cloudier (%)
1	92	8
2	92	8
3	91	9
4	91	9
5	91	9
6	91	9
7	91	9
8	91	9
9	90	10
10	90	10
11	90	10
12	90	10
13	89	11
14	88	12
15	88	12
16	88	12
17	88	12
18	88	12
19	88	12
20	88	12
21	87	13
22	87	13
23	87	13
24	87	13
25	87	13
26	86	14
27	86	14
28	84	16
29	84	16
30	84	16

Chance of precipitation in September

Any precipitation

Sun Valley gets around 0.4 in of rain over 2.5 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 8% and peaks near 10% on the wettest days.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Rain chance (%)	7	7	7	8	8	8	8	9	9	9	8	8	8	8	8	8	8	8	8	8	8	8	8	8	8	9	9	9	10	10

	Rain chance (%)
1	7
2	7
3	7
4	8
5	8
6	8
7	8
8	9
9	9
10	9
11	8
12	8
13	8
14	8
15	8
16	8
17	8
18	8
19	8
20	8
21	8
22	8
23	8
24	8
25	8
26	9
27	9
28	9
29	10
30	10

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.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Dry (%)	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100

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.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Wind speed (mph)	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4	4
Feels	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm

	Wind speed (mph)	Feels
1	4	calm
2	4	calm
3	4	calm
4	4	calm
5	4	calm
6	4	calm
7	4	calm
8	4	calm
9	4	calm
10	4	calm
11	4	calm
12	4	calm
13	4	calm
14	4	calm
15	4	calm
16	4	calm
17	4	calm
18	4	calm
19	4	calm
20	4	calm
21	4	calm
22	4	calm
23	4	calm
24	4	calm
25	4	calm
26	4	calm
27	4	calm
28	4	calm
29	4	calm
30	4	calm

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 5:59 AM, and sunset from 6:26 PM to 5:37 PM.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Daylight (h)	12.9	12.9	12.8	12.8	12.7	12.7	12.7	12.6	12.6	12.5	12.5	12.4	12.4	12.3	12.3	12.3	12.2	12.2	12.1	12.1	12.0	12.0	11.9	11.9	11.9	11.8	11.8	11.7	11.7	11.6
Sunrise (AM)	5:31	5:32	5:33	5:34	5:35	5:36	5:37	5:38	5:39	5:40	5:41	5:42	5:43	5:44	5:45	5:46	5:47	5:48	5:49	5:50	5:51	5:52	5:53	5:53	5:54	5:55	5:56	5:57	5:58	5:59
Sunset (PM)	6:26	6:25	6:23	6:21	6:20	6:18	6:16	6:15	6:13	6:11	6:10	6:08	6:06	6:05	6:03	6:01	5:59	5:58	5:56	5:54	5:53	5:51	5:49	5:47	5:46	5:44	5:42	5:41	5:39	5:37

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	12.9	5:31	6:26
2	12.9	5:32	6:25
3	12.8	5:33	6:23
4	12.8	5:34	6:21
5	12.7	5:35	6:20
6	12.7	5:36	6:18
7	12.7	5:37	6:16
8	12.6	5:38	6:15
9	12.6	5:39	6:13
10	12.5	5:40	6:11
11	12.5	5:41	6:10
12	12.4	5:42	6:08
13	12.4	5:43	6:06
14	12.3	5:44	6:05
15	12.3	5:45	6:03
16	12.3	5:46	6:01
17	12.2	5:47	5:59
18	12.2	5:48	5:58
19	12.1	5:49	5:56
20	12.1	5:50	5:54
21	12.0	5:51	5:53
22	12.0	5:52	5:51
23	11.9	5:53	5:49
24	11.9	5:53	5:47
25	11.9	5:54	5:46
26	11.8	5:55	5:44
27	11.8	5:56	5:42
28	11.7	5:57	5:41
29	11.7	5:58	5:39
30	11.6	5:59	5:37

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.08 kWh/m².

For context, solar energy here swings from a low near 2.42 kWh/m² to a high of 8.26 kWh/m² in June across the year — September's 6.08 kWh/m² falls in the middle.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Solar energy (kWh/m²)	6.8	6.7	6.7	6.6	6.6	6.5	6.5	6.5	6.4	6.3	6.3	6.3	6.2	6.2	6.1	6.1	6.0	6.0	5.9	5.8	5.8	5.8	5.7	5.6	5.6	5.5	5.5	5.4	5.3	5.3
Level	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Intense	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright	Bright

	Solar energy (kWh/m²)	Level
1	6.8	Intense
2	6.7	Intense
3	6.7	Intense
4	6.6	Intense
5	6.6	Intense
6	6.5	Intense
7	6.5	Intense
8	6.5	Intense
9	6.4	Intense
10	6.3	Intense
11	6.3	Intense
12	6.3	Intense
13	6.2	Intense
14	6.2	Intense
15	6.1	Intense
16	6.1	Intense
17	6.0	Intense
18	6.0	Bright
19	5.9	Bright
20	5.8	Bright
21	5.8	Bright
22	5.8	Bright
23	5.7	Bright
24	5.6	Bright
25	5.6	Bright
26	5.5	Bright
27	5.5	Bright
28	5.4	Bright
29	5.3	Bright
30	5.3	Bright

Planning a trip in September

Is September a good time to visit Sun Valley?

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

8.6

Sightseeing

1st-best month of the year

7.6

Beach & pool

3rd-best month of the year

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

What to pack for Sun Valley in September

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

In September, Sun Valley sees daytime highs around 77°F and nights near 50°F. Pack sun protection. Worth having: light clothes.

sun protectionlight clothes

UV index in Sun Valley 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 Sun Valley peaks around June 22 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near November 23 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
UV index (midday)	3	4	5	7	9	11	11	10	7	5	2	2
Level	Moderate	Moderate	Moderate	High	Very high	Extreme	Extreme	Very high	High	High	Moderate	Moderate

	UV index (midday)	Level
Jan	3	Moderate
Feb	4	Moderate
Mar	5	Moderate
Apr	7	High
May	9	Very high
Jun	11	Extreme
Jul	11	Extreme
Aug	10	Very high
Sep	7	High
Oct	5	High
Nov	2	Moderate
Dec	2	Moderate

Air quality in Sun Valley 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 Sun Valley is worst in July — around 51 µg/m³ PM2.5 (poor), about 8.5× the cleanest month (December, 6 µg/m³).

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

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
PM2.5 (µg/m³)	7	8	10	10	10	10	51	42	45	15	7	6
Level	Good	Good	Good	Good	Good	Good	Poor	Poor	Poor	Moderate	Good	Good

	PM2.5 (µg/m³)	Level
Jan	7	Good
Feb	8	Good
Mar	10	Good
Apr	10	Good
May	10	Good
Jun	10	Good
Jul	51	Poor
Aug	42	Poor
Sep	45	Poor
Oct	15	Moderate
Nov	7	Good
Dec	6	Good

Location & terrain

Where is Sun Valley?

Sun Valley sits at 39.6°N, 119.8°W, 4,724 ft above sea level, in United States. The nearest listed city is Sparks, 4.3 mi away.

Topography around Sun Valley

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

Within 2 miles, the terrain around Sun Valley has significant variations in elevation — a maximum elevation change of 1,112 ft around an average of 4,898 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,911 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 7,779 ft.

The land around Sun Valley is covered by grassland (51%) and artificial surfaces (31%) within 2 miles, grassland (55%) and artificial surfaces (22%) within 10 miles, and grassland (40%) and trees (29%) within 50 miles.

2 miles

1,112 ft

grassland 51%

10 miles

3,911 ft

grassland 55%

50 miles

7,779 ft

grassland 40%

treesshrubsgrasslandcroplandartificial surfacesbare terrainwater

← August Sun Valley year-round climate October →Best places to visit in September

September weather nearby: Sparks 4.3 mi · Reno 5.0 mi · Spanish Springs 5.0 mi · Fernley 28 mi · Truckee 29 mi · Carson City 30 mi · Lake Tahoe 47 mi · Susanville 73 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

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 Sun Valley (39.5963°, -119.776°, elevation 4,724 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).

	Avg high (°F)	Avg low (°F)
1	82	54
2	82	53
3	82	53
4	81	53
5	81	53
6	81	53
7	80	52
8	80	52
9	80	52
10	79	51
11	79	51
12	78	51
13	78	51
14	78	50
15	77	50
16	77	50
17	76	50
18	76	49
19	76	49
20	76	49
21	75	49
22	75	48
23	74	48
24	74	48
25	74	47
26	73	47
27	73	47
28	73	46
29	72	46
30	72	46

	Clearer (%)	Cloudier (%)
1	92	8
2	92	8
3	91	9
4	91	9
5	91	9
6	91	9
7	91	9
8	91	9
9	90	10
10	90	10
11	90	10
12	90	10
13	89	11
14	88	12
15	88	12
16	88	12
17	88	12
18	88	12
19	88	12
20	88	12
21	87	13
22	87	13
23	87	13
24	87	13
25	87	13
26	86	14
27	86	14
28	84	16
29	84	16
30	84	16

	Rain chance (%)
1	7
2	7
3	7
4	8
5	8
6	8
7	8
8	9
9	9
10	9
11	8
12	8
13	8
14	8
15	8
16	8
17	8
18	8
19	8
20	8
21	8
22	8
23	8
24	8
25	8
26	9
27	9
28	9
29	10
30	10

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100

	Avg high (°F)	Avg low (°F)
1	82	54
2	82	53
3	82	53
4	81	53
5	81	53
6	81	53
7	80	52
8	80	52
9	80	52
10	79	51
11	79	51
12	78	51
13	78	51
14	78	50
15	77	50
16	77	50
17	76	50
18	76	49
19	76	49
20	76	49
21	75	49
22	75	48
23	74	48
24	74	48
25	74	47
26	73	47
27	73	47
28	73	46
29	72	46
30	72	46

	Clearer (%)	Cloudier (%)
1	92	8
2	92	8
3	91	9
4	91	9
5	91	9
6	91	9
7	91	9
8	91	9
9	90	10
10	90	10
11	90	10
12	90	10
13	89	11
14	88	12
15	88	12
16	88	12
17	88	12
18	88	12
19	88	12
20	88	12
21	87	13
22	87	13
23	87	13
24	87	13
25	87	13
26	86	14
27	86	14
28	84	16
29	84	16
30	84	16

	Rain chance (%)
1	7
2	7
3	7
4	8
5	8
6	8
7	8
8	9
9	9
10	9
11	8
12	8
13	8
14	8
15	8
16	8
17	8
18	8
19	8
20	8
21	8
22	8
23	8
24	8
25	8
26	9
27	9
28	9
29	10
30	10

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100

	Avg high (°F)	Avg low (°F)
1	82	54
2	82	53
3	82	53
4	81	53
5	81	53
6	81	53
7	80	52
8	80	52
9	80	52
10	79	51
11	79	51
12	78	51
13	78	51
14	78	50
15	77	50
16	77	50
17	76	50
18	76	49
19	76	49
20	76	49
21	75	49
22	75	48
23	74	48
24	74	48
25	74	47
26	73	47
27	73	47
28	73	46
29	72	46
30	72	46

	Clearer (%)	Cloudier (%)
1	92	8
2	92	8
3	91	9
4	91	9
5	91	9
6	91	9
7	91	9
8	91	9
9	90	10
10	90	10
11	90	10
12	90	10
13	89	11
14	88	12
15	88	12
16	88	12
17	88	12
18	88	12
19	88	12
20	88	12
21	87	13
22	87	13
23	87	13
24	87	13
25	87	13
26	86	14
27	86	14
28	84	16
29	84	16
30	84	16

	Rain chance (%)
1	7
2	7
3	7
4	8
5	8
6	8
7	8
8	9
9	9
10	9
11	8
12	8
13	8
14	8
15	8
16	8
17	8
18	8
19	8
20	8
21	8
22	8
23	8
24	8
25	8
26	9
27	9
28	9
29	10
30	10

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100