Sunnyvale Weather in September
Average highs run from 91°F on September 1 to 83°F on September 30, and lows from 71°F to 61°F. Normal precipitation for the month is 3.10 in over about 6 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
- 87°F
- Average low
- 66°F
- Precipitation
- 3.10 in
- Record high
- 111°FSep 4, 2000
- Record low
- 42°FSep 22, 1983
- Chance of a freeze
- 0%
- Days of 90°F or more
- 15.0
- Daylight
- 12 h 50 min to 11 h 52 min
- Cloud cover
- 42%
- Humidity
- 63%
- Dew point
- 62°F
- Wind
- 8.3 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 | 91°F | 71°F | 110°F 1985 | 59°F 1987 | 20% | 0% |
| Sep 2 | 90°F | 70°F | 109°F 2000 | 59°F 1987 | 20% | 0% |
| Sep 3 | 90°F | 70°F | 110°F 2000 | 59°F 1974 | 21% | 0% |
| Sep 4 | 90°F | 70°F | 111°F 2000 | 55°F 1974 | 20% | 0% |
| Sep 5 | 90°F | 70°F | 105°F 2023 | 54°F 1974 | 20% | 0% |
| Sep 6 | 89°F | 69°F | 107°F 2023 | 53°F 2017 | 20% | 0% |
| Sep 7 | 89°F | 69°F | 109°F 2023 | 53°F 2017 | 20% | 0% |
| Sep 8 | 89°F | 69°F | 111°F 2023 | 55°F 2017 | 20% | 0% |
| Sep 9 | 89°F | 68°F | 102°F 1972 | 56°F 2004 | 20% | 0% |
| Sep 10 | 88°F | 68°F | 100°F 1984 | 54°F 2021 | 20% | 0% |
| Sep 11 | 88°F | 68°F | 100°F 1963 | 53°F 1968 | 20% | 0% |
| Sep 12 | 88°F | 67°F | 105°F 2011 | 55°F 1968 | 20% | 0% |
| Sep 13 | 87°F | 67°F | 109°F 2011 | 51°F 1969 | 20% | 0% |
| Sep 14 | 87°F | 67°F | 103°F 1965 | 52°F 1989 | 20% | 0% |
| Sep 15 | 87°F | 66°F | 101°F 1980 | 51°F 1993 | 20% | 0% |
| Sep 16 | 87°F | 66°F | 102°F 1980 | 51°F 1979 | 20% | 0% |
| Sep 17 | 86°F | 66°F | 99°F 1997 | 50°F 1981 | 20% | 0% |
| Sep 18 | 86°F | 65°F | 101°F 1980 | 46°F 1981 | 20% | 0% |
| Sep 19 | 86°F | 65°F | 100°F 2016 | 51°F 1991 | 20% | 0% |
| Sep 20 | 86°F | 64°F | 102°F 2021 | 47°F 1971 | 20% | 0% |
| Sep 21 | 85°F | 64°F | 101°F 2005 | 47°F 1983 | 19% | 0% |
| Sep 22 | 85°F | 64°F | 102°F 2005 | 42°F 1983 | 19% | 0% |
| Sep 23 | 85°F | 63°F | 100°F 2005 | 43°F 1994 | 19% | 0% |
| Sep 24 | 84°F | 63°F | 102°F 2023 | 46°F 1989 | 19% | 0% |
| Sep 25 | 84°F | 63°F | 103°F 2005 | 46°F 1989 | 19% | 0% |
| Sep 26 | 84°F | 62°F | 103°F 2005 | 45°F 2000 | 19% | 0% |
| Sep 27 | 84°F | 62°F | 102°F 1977 | 50°F 1985 | 19% | 0% |
| Sep 28 | 83°F | 61°F | 102°F 2005 | 45°F 1967 | 19% | 0% |
| Sep 29 | 83°F | 61°F | 102°F 2011 | 43°F 1967 | 19% | 0% |
| Sep 30 | 83°F | 61°F | 98°F 1977 | 43°F 1984 | 19% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (CDT).
- September 1
- sunrise 7:01 AM, sunset 7:51 PM
- September 30
- sunrise 7:20 AM, sunset 7:12 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00415094 (Lavon Dam), public domain. Records: NOAA GHCN-Daily, station USC00413133, 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.