Boundary County Weather in September
Average highs run from 80°F on September 1 to 66°F on September 30, and lows from 49°F to 40°F. Normal precipitation for the month is 1.02 in over about 7 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
- 73°F
- Average low
- 45°F
- Precipitation
- 1.02 in
- Record high
- 98°FSep 3, 2025
- Record low
- 15°FSep 23, 2000
- Chance of a freeze
- 39%
- Days of 90°F or more
- 1.0
- Daylight
- 13 h 25 min to 11 h 42 min
- Cloud cover
- 55%
- Humidity
- 65%
- Dew point
- 38°F
- Wind
- 3.8 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.
| Date | Normal high | Normal low | Record high | Record low | Chance wet | Chance of snow |
|---|---|---|---|---|---|---|
| Sep 1 | 80°F | 49°F | 94°F 1950 | 32°F 1913 | 19% | 0% |
| Sep 2 | 79°F | 48°F | 96°F 1938 | 28°F 1991 | 19% | 0% |
| Sep 3 | 79°F | 48°F | 98°F 2025 | 30°F 1991 | 20% | 0% |
| Sep 4 | 78°F | 48°F | 96°F 2025 | 33°F 1956 | 20% | 0% |
| Sep 5 | 78°F | 48°F | 96°F 1988 | 23°F 1991 | 20% | 0% |
| Sep 6 | 78°F | 47°F | 96°F 1944 | 32°F 1965 | 21% | 0% |
| Sep 7 | 77°F | 47°F | 96°F 1944 | 30°F 1911 | 21% | 0% |
| Sep 8 | 77°F | 47°F | 92°F 1944 | 29°F 1962 | 21% | 0% |
| Sep 9 | 76°F | 46°F | 97°F 1909 | 30°F 1910 | 21% | 0% |
| Sep 10 | 76°F | 46°F | 95°F 1944 | 30°F 1913 | 21% | 0% |
| Sep 11 | 76°F | 46°F | 95°F 1944 | 29°F 1964 | 22% | 0% |
| Sep 12 | 75°F | 46°F | 94°F 1944 | 23°F 1970 | 22% | 0% |
| Sep 13 | 75°F | 45°F | 97°F 2013 | 26°F 1993 | 22% | 0% |
| Sep 14 | 74°F | 45°F | 92°F 2013 | 25°F 1970 | 22% | 0% |
| Sep 15 | 74°F | 45°F | 90°F 2001 | 24°F 1970 | 22% | 0% |
| Sep 16 | 73°F | 45°F | 90°F 2013 | 26°F 1973 | 23% | 0% |
| Sep 17 | 73°F | 44°F | 89°F 1981 | 27°F 1971 | 23% | 0% |
| Sep 18 | 73°F | 44°F | 92°F 1981 | 26°F 1945 | 23% | 0% |
| Sep 19 | 72°F | 44°F | 88°F 2025 | 25°F 1943 | 23% | 0% |
| Sep 20 | 72°F | 43°F | 86°F 1967 | 25°F 1983 | 24% | 0% |
| Sep 21 | 71°F | 43°F | 89°F 1967 | 28°F 1971 | 24% | 0% |
| Sep 22 | 71°F | 43°F | 87°F 1950 | 26°F 2000 | 24% | 0% |
| Sep 23 | 70°F | 42°F | 85°F 1987 | 15°F 2000 | 24% | 0% |
| Sep 24 | 69°F | 42°F | 86°F 2011 | 22°F 1984 | 24% | 0% |
| Sep 25 | 69°F | 42°F | 86°F 2024 | 24°F 1910 | 25% | 0% |
| Sep 26 | 68°F | 41°F | 89°F 1952 | 29°F 1908 | 25% | 0% |
| Sep 27 | 68°F | 41°F | 85°F 1967 | 25°F 1961 | 25% | 0% |
| Sep 28 | 67°F | 41°F | 87°F 1909 | 21°F 1984 | 25% | 0% |
| Sep 29 | 67°F | 40°F | 83°F 1963 | 21°F 1985 | 26% | 0% |
| Sep 30 | 66°F | 40°F | 80°F 1976 | 24°F 1985 | 26% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (PDT).
- September 1
- sunrise 6:03 AM, sunset 7:28 PM
- September 30
- sunrise 6:44 AM, sunset 6:26 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00101079 (Bonners Ferry), public domain. Records: NOAA GHCN-Daily, station USC00101079, 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.