Lassen County Weather in September
Average highs run from 84°F on September 1 to 75°F on September 30, and lows from 49°F to 41°F. Normal precipitation for the month is 0.24 in over about 1 wet days.
September day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
September at a glance
- Average high
- 80°F
- Average low
- 45°F
- Precipitation
- 0.24 in
- Record high
- 101°FSep 2, 1950
- Record low
- 18°FSep 30, 1950
- Chance of a freeze
- 22%
- Days of 90°F or more
- 1.9
- Daylight
- 13 h 04 min to 11 h 48 min
- Cloud cover
- 26%
- Humidity
- 36%
- Dew point
- 29°F
- Wind
- 5.4 mph
Every day of the month
A wet day has at least 0.01 inch of precipitation.
| Date | Normal high | Normal low | Record high | Record low | Chance wet |
|---|---|---|---|---|---|
| Sep 1 | 84°F | 49°F | 98°F 1950 | 34°F 1951 | 2% |
| Sep 2 | 84°F | 49°F | 101°F 1950 | 27°F 1964 | 2% |
| Sep 3 | 84°F | 49°F | 100°F 1955 | 32°F 1964 | 2% |
| Sep 4 | 84°F | 48°F | 98°F 1955 | 33°F 1954 | 2% |
| Sep 5 | 83°F | 48°F | 98°F 1955 | 34°F 1900 | 2% |
| Sep 6 | 83°F | 48°F | 98°F 2022 | 34°F 1911 | 2% |
| Sep 7 | 83°F | 48°F | 100°F 2022 | 32°F 1992 | 2% |
| Sep 8 | 83°F | 47°F | 97°F 2022 | 32°F 1901 | 2% |
| Sep 9 | 82°F | 47°F | 96°F 1944 | 32°F 1927 | 2% |
| Sep 10 | 82°F | 47°F | 96°F 1948 | 29°F 1994 | 3% |
| Sep 11 | 82°F | 47°F | 95°F 1944 | 31°F 1985 | 3% |
| Sep 12 | 82°F | 46°F | 94°F 1913 | 26°F 1994 | 3% |
| Sep 13 | 81°F | 46°F | 96°F 1947 | 23°F 1914 | 3% |
| Sep 14 | 81°F | 46°F | 101°F 1929 | 22°F 1970 | 3% |
| Sep 15 | 81°F | 46°F | 96°F 1937 | 29°F 1985 | 3% |
| Sep 16 | 80°F | 45°F | 96°F 1932 | 30°F 2021 | 3% |
| Sep 17 | 80°F | 45°F | 96°F 1929 | 28°F 1949 | 3% |
| Sep 18 | 80°F | 45°F | 96°F 1929 | 23°F 1965 | 4% |
| Sep 19 | 79°F | 45°F | 90°F 1929 | 23°F 1947 | 4% |
| Sep 20 | 79°F | 44°F | 92°F 1913 | 26°F 1965 | 4% |
| Sep 21 | 78°F | 44°F | 91°F 1936 | 26°F 1993 | 4% |
| Sep 22 | 78°F | 44°F | 90°F 1949 | 26°F 1968 | 4% |
| Sep 23 | 78°F | 43°F | 90°F 1949 | 20°F 2017 | 4% |
| Sep 24 | 77°F | 43°F | 92°F 1943 | 23°F 1958 | 4% |
| Sep 25 | 77°F | 43°F | 92°F 1967 | 23°F 1948 | 4% |
| Sep 26 | 76°F | 42°F | 89°F 1963 | 27°F 1955 | 5% |
| Sep 27 | 76°F | 42°F | 92°F 2009 | 24°F 1948 | 5% |
| Sep 28 | 76°F | 42°F | 91°F 2010 | 25°F 1959 | 5% |
| Sep 29 | 75°F | 41°F | 89°F 1963 | 22°F 1954 | 5% |
| Sep 30 | 75°F | 41°F | 90°F 1992 | 18°F 1950 | 5% |
Chance of rain
- Chance of a wet day
Sunrise and sunset
Times for 2026, local time (PDT).
- September 1
- sunrise 6:30 AM, sunset 7:34 PM
- September 30
- sunrise 6:58 AM, sunset 6:46 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00048702 (Susanville 2SW), public domain. Records: NOAA GHCN-Daily, station USC00048702, 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.