Lewis and Clark County climate

Lewis and Clark County Weather in September

NOAA 1991-2020 normals for Rogers Pass 9 Nne, 10.7 km from Lewis and Clark County

Average highs run from 76°F on September 1 to 64°F on September 30, and lows from 45°F to 37°F. Normal precipitation for the month is 1.65 in over about 6 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 Lewis and Clark County, in °F, with the record for each date.020406080100151015202530
  • Normal low
  • Normal high
  • Record high
  • Record low

September at a glance

Average high
70°F
Average low
41°F
Precipitation
1.65 in
Record high
95°FSep 1, 1991
Record low
6°FSep 30, 2019
Chance of a freeze
91%
Days of 90°F or more
0.8
Daylight
13 h 20 min to 11 h 44 min
Cloud cover
55%
Humidity
61%
Dew point
35°F
Wind
5.1 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 176°F45°F95°F 199129°F 200620%
Sep 275°F44°F92°F 199832°F 201020%
Sep 375°F44°F94°F 199829°F 201120%
Sep 475°F44°F94°F 199829°F 199220%
Sep 574°F44°F94°F 199829°F 196520%
Sep 674°F43°F95°F 199829°F 196520%
Sep 774°F43°F89°F 201726°F 202020%
Sep 873°F43°F93°F 199828°F 197620%
Sep 973°F43°F89°F 196631°F 198920%
Sep 1073°F42°F89°F 196830°F 196521%
Sep 1172°F42°F89°F 196622°F 197021%
Sep 1272°F42°F89°F 199023°F 198921%
Sep 1371°F41°F85°F 200622°F 197021%
Sep 1471°F41°F85°F 198715°F 197021%
Sep 1571°F41°F91°F 200021°F 197321%
Sep 1670°F41°F94°F 200015°F 196521%
Sep 1770°F40°F90°F 200010°F 196522%
Sep 1869°F40°F93°F 198115°F 196522%
Sep 1969°F40°F90°F 198123°F 199122%
Sep 2068°F40°F88°F 200925°F 198322%
Sep 2168°F39°F89°F 196625°F 196822%
Sep 2268°F39°F89°F 198721°F 200022%
Sep 2367°F39°F89°F 20119°F 200022%
Sep 2467°F38°F90°F 200911°F 200022%
Sep 2566°F38°F91°F 200121°F 197223%
Sep 2666°F38°F89°F 200126°F 196523%
Sep 2765°F38°F84°F 196721°F 196523%
Sep 2865°F37°F89°F 196719°F 198523%
Sep 2964°F37°F84°F 199114°F 198423%
Sep 3064°F37°F86°F 20116°F 201923%

Chance of rain

The chance of at least 0.01 inch of precipitation on each date at Lewis and Clark County, in percent, and of at least 0.1 inch of snowfall.05101520251102030
  • Chance of a wet day
  • Chance of snowfall

Sunrise and sunset

Times for 2026, local time (MDT).

September 1
sunrise 6:49 AM, sunset 8:09 PM
September 30
sunrise 7:27 AM, sunset 7:11 PM

Every day of September: sun and moon

Other months

Sources

Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00247159 (Rogers Pass 9 Nne), public domain. Records: NOAA GHCN-Daily, station USC00247159, 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.