Lake Oswego Weather in September
Average highs run from 79°F on September 1 to 70°F on September 30, and lows from 57°F to 52°F. Normal precipitation for the month is 1.58 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
- 75°F
- Average low
- 55°F
- Precipitation
- 1.58 in
- Record high
- 105°FSep 2, 1988
- Record low
- 34°FSep 17, 1965
- Chance of a freeze
- 0%
- Days of 90°F or more
- 1.4
- Daylight
- 13 h 16 min to 11 h 44 min
- Cloud cover
- 49%
- Humidity
- 68%
- Dew point
- 48°F
- Wind
- 4.5 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 | 79°F | 57°F | 98°F 1988 | 44°F 1973 | 17% | 0% |
| Sep 2 | 78°F | 57°F | 105°F 1988 | 42°F 1960 | 17% | 0% |
| Sep 3 | 78°F | 57°F | 95°F 2017 | 45°F 1980 | 18% | 0% |
| Sep 4 | 78°F | 57°F | 98°F 1955 | 43°F 1956 | 18% | 0% |
| Sep 5 | 78°F | 57°F | 102°F 2024 | 44°F 1956 | 18% | 0% |
| Sep 6 | 78°F | 57°F | 97°F 1958 | 45°F 1960 | 19% | 0% |
| Sep 7 | 77°F | 57°F | 99°F 1981 | 42°F 1992 | 19% | 0% |
| Sep 8 | 77°F | 57°F | 93°F 1993 | 42°F 1960 | 20% | 0% |
| Sep 9 | 77°F | 56°F | 94°F 1948 | 42°F 1962 | 20% | 0% |
| Sep 10 | 77°F | 56°F | 98°F 1944 | 42°F 1952 | 21% | 0% |
| Sep 11 | 77°F | 56°F | 95°F 2013 | 43°F 1964 | 21% | 0% |
| Sep 12 | 76°F | 56°F | 92°F 1945 | 41°F 1955 | 22% | 0% |
| Sep 13 | 76°F | 56°F | 93°F 1988 | 37°F 1970 | 22% | 0% |
| Sep 14 | 76°F | 56°F | 92°F 1938 | 42°F 1969 | 23% | 0% |
| Sep 15 | 76°F | 55°F | 96°F 1981 | 40°F 1970 | 23% | 0% |
| Sep 16 | 75°F | 55°F | 92°F 1994 | 41°F 1965 | 24% | 0% |
| Sep 17 | 75°F | 55°F | 94°F 1938 | 34°F 1965 | 24% | 0% |
| Sep 18 | 75°F | 55°F | 93°F 1991 | 36°F 1965 | 24% | 0% |
| Sep 19 | 74°F | 55°F | 93°F 1974 | 39°F 1957 | 25% | 0% |
| Sep 20 | 74°F | 54°F | 96°F 1952 | 39°F 1957 | 25% | 0% |
| Sep 21 | 74°F | 54°F | 94°F 1952 | 39°F 1964 | 26% | 0% |
| Sep 22 | 73°F | 54°F | 93°F 1952 | 34°F 1961 | 26% | 0% |
| Sep 23 | 73°F | 54°F | 94°F 1974 | 40°F 2000 | 26% | 0% |
| Sep 24 | 72°F | 54°F | 96°F 1974 | 36°F 1970 | 27% | 0% |
| Sep 25 | 72°F | 53°F | 94°F 1991 | 38°F 1955 | 27% | 0% |
| Sep 26 | 72°F | 53°F | 92°F 1967 | 38°F 1961 | 28% | 0% |
| Sep 27 | 71°F | 53°F | 95°F 2003 | 37°F 1945 | 28% | 0% |
| Sep 28 | 71°F | 53°F | 89°F 1989 | 37°F 1983 | 29% | 0% |
| Sep 29 | 70°F | 52°F | 89°F 1987 | 37°F 1954 | 30% | 0% |
| Sep 30 | 70°F | 52°F | 88°F 1987 | 35°F 1954 | 30% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (PDT).
- September 1
- sunrise 6:32 AM, sunset 7:48 PM
- September 30
- sunrise 7:08 AM, sunset 6:52 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00356749 (Portland Kgw-TV), public domain. Records: NOAA GHCN-Daily, station USW00024229, 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.