Sun Valley climate

Sun Valley Weather in September

NOAA 1991-2020 normals for Ketchum RS, 1.6 km from Sun Valley

Average highs run from 74°F on September 1 to 63°F on September 30, and lows from 40°F to 33°F. Normal precipitation for the month is 1.01 in over about 4 wet days.

September day by day

The normal high and low for each date, and the record, in °F.

Normal daily high and low temperature at Sun Valley, in °F, with the record for each date.20406080100151015202530
  • Normal low
  • Normal high
  • Record high
  • Record low

September at a glance

Average high
69°F
Average low
36°F
Precipitation
1.01 in
Record high
96°FSep 5, 2020
Record low
26°FSep 30, 2019
Chance of a freeze
97%
Daylight
13 h 12 min to 11 h 46 min
Cloud cover
39%
Humidity
41%
Dew point
29°F
Wind
7.2 mph

Every day of the month

A wet day has at least 0.01 inch of precipitation; snow means at least 0.1 inch of snowfall.

DateNormal highNormal lowRecord highRecord lowChance wetChance of snow
Sep 174°F40°F94°F 202234°F 202014%0%
Sep 274°F39°F92°F 201741°F 201414%0%
Sep 374°F39°F95°F 201740°F 201414%0%
Sep 473°F39°F93°F 202238°F 201414%0%
Sep 573°F39°F96°F 202037°F 201614%0%
Sep 673°F38°F96°F 202233°F 201514%0%
Sep 772°F38°F96°F 202237°F 201514%0%
Sep 872°F38°F95°F 202240°F 202015%0%
Sep 972°F38°F92°F 202134°F 202015%0%
Sep 1071°F37°F89°F 201539°F 201615%0%
Sep 1171°F37°F86°F 201534°F 201415%0%
Sep 1271°F37°F88°F 201533°F 201415%0%
Sep 1370°F37°F86°F 201536°F 201615%0%
Sep 1470°F37°F87°F 202036°F 202615%0%
Sep 1569°F36°F84°F 201438°F 202615%0%
Sep 1669°F36°F86°F 201432°F 201815%0%
Sep 1769°F36°F87°F 201437°F 201815%0%
Sep 1868°F36°F83°F 202335°F 201515%0%
Sep 1968°F35°F80°F 201436°F 201715%0%
Sep 2067°F35°F83°F 202533°F 202115%0%
Sep 2167°F35°F80°F 201534°F 202115%0%
Sep 2267°F35°F82°F 201537°F 201915%0%
Sep 2366°F34°F80°F 201531°F 201715%0%
Sep 2466°F34°F85°F 201435°F 201715%0%
Sep 2565°F34°F86°F 201534°F 201815%0%
Sep 2665°F34°F84°F 202436°F 201815%1%
Sep 2765°F33°F83°F 202234°F 202015%1%
Sep 2864°F33°F87°F 202434°F 202015%1%
Sep 2964°F33°F86°F 202429°F 202115%1%
Sep 3063°F33°F79°F 201526°F 201915%1%

Chance of rain

The chance of at least 0.01 inch of precipitation on each date at Sun Valley, in percent, and of at least 0.1 inch of snowfall.051015201102030
  • Chance of a wet day
  • Chance of snowfall

Sunrise and sunset

Times for 2026, local time (MDT).

September 1
sunrise 7:01 AM, sunset 8:13 PM
September 30
sunrise 7:34 AM, sunset 7:20 PM

Every day of September: sun and moon

Other months

Sources

Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00104845 (Ketchum RS), public domain. Records: NOAA GHCN-Daily, station USC00100774, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-24. Sun and moon: computed with the NOAA solar equations and Meeus.