Whatcom County Weather in September
Average highs run from 73°F on September 1 to 63°F on September 30, and lows from 50°F to 45°F. Normal precipitation for the month is 4.83 in over about 11 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
- 69°F
- Average low
- 47°F
- Precipitation
- 4.83 in
- Record high
- 89°FSep 14, 1951
- Record low
- 28°FSep 27, 1972
- Chance of a freeze
- 2%
- Daylight
- 13 h 24 min to 11 h 42 min
- Cloud cover
- 57%
- Humidity
- 79%
- Dew point
- 47°F
- Wind
- 3.1 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.
| Date | Normal high | Normal low | Record high | Record low | Chance wet | Chance of snow |
|---|---|---|---|---|---|---|
| Sep 1 | 73°F | 50°F | 82°F 1952 | 39°F 1960 | 30% | 0% |
| Sep 2 | 73°F | 49°F | 87°F 1988 | 39°F 1984 | 31% | 0% |
| Sep 3 | 72°F | 49°F | 87°F 1988 | 40°F 1958 | 31% | 0% |
| Sep 4 | 72°F | 49°F | 87°F 2017 | 38°F 1952 | 32% | 0% |
| Sep 5 | 72°F | 49°F | 86°F 1973 | 39°F 1956 | 32% | 0% |
| Sep 6 | 72°F | 49°F | 84°F 1986 | 40°F 2005 | 33% | 0% |
| Sep 7 | 71°F | 49°F | 87°F 1981 | 40°F 1984 | 33% | 0% |
| Sep 8 | 71°F | 49°F | 83°F 1989 | 39°F 1962 | 34% | 0% |
| Sep 9 | 71°F | 48°F | 88°F 1963 | 38°F 1959 | 34% | 0% |
| Sep 10 | 71°F | 48°F | 85°F 2020 | 40°F 1959 | 35% | 0% |
| Sep 11 | 70°F | 48°F | 83°F 1975 | 39°F 1988 | 35% | 0% |
| Sep 12 | 70°F | 48°F | 80°F 1975 | 33°F 1949 | 36% | 0% |
| Sep 13 | 70°F | 48°F | 83°F 1957 | 33°F 1970 | 36% | 0% |
| Sep 14 | 69°F | 48°F | 89°F 1951 | 39°F 1952 | 37% | 0% |
| Sep 15 | 69°F | 48°F | 87°F 1951 | 35°F 1969 | 37% | 0% |
| Sep 16 | 69°F | 47°F | 85°F 2025 | 36°F 1992 | 38% | 0% |
| Sep 17 | 68°F | 47°F | 81°F 1991 | 37°F 1971 | 38% | 0% |
| Sep 18 | 68°F | 47°F | 78°F 1991 | 37°F 1972 | 39% | 0% |
| Sep 19 | 68°F | 47°F | 85°F 1974 | 33°F 1957 | 39% | 0% |
| Sep 20 | 67°F | 47°F | 89°F 1974 | 35°F 1968 | 40% | 0% |
| Sep 21 | 67°F | 47°F | 85°F 1952 | 32°F 1955 | 40% | 0% |
| Sep 22 | 67°F | 46°F | 83°F 1975 | 34°F 1955 | 41% | 0% |
| Sep 23 | 66°F | 46°F | 79°F 1957 | 33°F 2000 | 41% | 0% |
| Sep 24 | 66°F | 46°F | 82°F 1974 | 34°F 1955 | 42% | 0% |
| Sep 25 | 66°F | 46°F | 76°F 1991 | 31°F 1972 | 42% | 0% |
| Sep 26 | 65°F | 46°F | 79°F 1949 | 36°F 1951 | 43% | 0% |
| Sep 27 | 65°F | 45°F | 81°F 1963 | 28°F 1972 | 43% | 0% |
| Sep 28 | 64°F | 45°F | 87°F 2003 | 33°F 1983 | 44% | 0% |
| Sep 29 | 64°F | 45°F | 77°F 2008 | 32°F 1954 | 44% | 0% |
| Sep 30 | 63°F | 45°F | 77°F 1987 | 32°F 1950 | 45% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (PDT).
- September 1
- sunrise 6:25 AM, sunset 7:49 PM
- September 30
- sunrise 7:06 AM, sunset 6:48 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00458715 (Upper Baker Dam), public domain. Records: NOAA GHCN-Daily, station USW00024217, 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.