Grass Valley weather in September: Grass Valley, California: normal highs, lows, rain and records for September
Grass Valley in September has a normal high of 82°F and a normal low of 52°F, a daily mean of 67°F, falling from 86°F on the 1st to 78°F by the 30th. Measurable precipitation falls on 2 days in a normal September, 0.44 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 28°C and low of 11°C, 11 mm of precipitation in September.
- NOAA stationGrass Valley #2
- Station IDUSC00043573
- Location39.20°N 121.07°W
- Elevation2,400 ft (732 m)
- Population14,085
- Jan 54° 33°
- Feb 55° 34°
- Mar 58° 37°
- Apr 63° 40°
- May 71° 47°
- Jun 80° 53°
- Jul 88° 58°
- Aug 87° 57°
- Sep 82° 52°
- Oct 72° 44°
- Nov 60° 37°
- Dec 53° 33°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Grass Valley in September?
The normal high is 82°F and the normal low 52°F, for a daily mean of 67.2°F. September is 4.9°F cooler than August and 9.0°F warmer than October. September is the 3rd warmest month of the year in Grass Valley and the 10th wettest. Across the month the normal high falls 8°F, from 86°F on September 1 to 78°F on September 30. From one year to the next September's mean temperature typically moves about 2.1°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 65°F and 69°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 9%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 86°F | 55°F | 3% | 1% |
| September 8 | 84°F | 54°F | 4% | 2% |
| September 15 | 83°F | 52°F | 5% | 3% |
| September 22 | 81°F | 51°F | 7% | 4% |
| September 30 | 78°F | 49°F | 9% | 6% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 86°F | 55°F | 3% | 1% | 13 h 10 min |
| September 2 | 85°F | 55°F | 3% | 2% | 13 h |
| September 3 | 85°F | 54°F | 3% | 2% | 13 h |
| September 4 | 85°F | 54°F | 3% | 2% | 13 h |
| September 5 | 85°F | 54°F | 4% | 2% | 13 h |
| September 6 | 85°F | 54°F | 4% | 2% | 12 h 50 min |
| September 7 | 85°F | 54°F | 4% | 2% | 12 h 50 min |
| September 8 | 84°F | 54°F | 4% | 2% | 12 h 50 min |
| September 9 | 84°F | 54°F | 4% | 2% | 12 h 50 min |
| September 10 | 84°F | 53°F | 4% | 2% | 12 h 40 min |
| September 11 | 84°F | 53°F | 4% | 3% | 12 h 40 min |
| September 12 | 83°F | 53°F | 5% | 3% | 12 h 40 min |
| September 13 | 83°F | 53°F | 5% | 3% | 12 h 40 min |
| September 14 | 83°F | 53°F | 5% | 3% | 12 h 30 min |
| September 15 | 83°F | 52°F | 5% | 3% | 12 h 30 min |
| September 16 | 82°F | 52°F | 5% | 3% | 12 h 30 min |
| September 17 | 82°F | 52°F | 6% | 3% | 12 h 30 min |
| September 18 | 82°F | 52°F | 6% | 4% | 12 h 20 min |
| September 19 | 82°F | 52°F | 6% | 4% | 12 h 20 min |
| September 20 | 81°F | 51°F | 6% | 4% | 12 h 20 min |
| September 21 | 81°F | 51°F | 7% | 4% | 12 h 20 min |
| September 22 | 81°F | 51°F | 7% | 4% | 12 h 10 min |
| September 23 | 81°F | 51°F | 7% | 5% | 12 h 10 min |
| September 24 | 80°F | 50°F | 8% | 5% | 12 h 10 min |
| September 25 | 80°F | 50°F | 8% | 5% | 12 h 10 min |
| September 26 | 80°F | 50°F | 8% | 5% | 12 h |
| September 27 | 79°F | 50°F | 8% | 5% | 12 h |
| September 28 | 79°F | 49°F | 9% | 6% | 12 h |
| September 29 | 79°F | 49°F | 9% | 6% | 11 h 50 min |
| September 30 | 78°F | 49°F | 9% | 6% | 11 h 50 min |
- Normal high
- 82°FSeptember average
- Normal low
- 52°FSeptember average
- Precipitation
- 0.44 inmonth total
- Days with precipitation
- 20.01 inch or more
- Days at 90°F or more
- 5
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 28
- Days at 80°F or more
- 21
- Sunshine
- 95%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USC00043573; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Grass Valley in September?
On a given September day the chance of 0.01 inch or more is 6% on average, highest around September 30 (9%). In all, 0.44 in falls on 2 days of a normal September.
In a normal September in Grass Valley, 5 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USC00043573.
What are the records for September in Grass Valley?
The warmest September temperature on this station's record (since 1966) is 108°F, on September 7, 2022; the coldest is 35°F, on September 28, 1986. The wettest September brought 5.87 in (1986).
The September mean against the 1991-2020 normal of 67.2°F: 2021 70.0°F (+2.8), 2022 70.9°F (+3.7), 2023 65.3°F (−1.9), 2024 70.0°F (+2.8), 2025 69.0°F (+1.8), 2026 64.6°F (−2.6). 4 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 70.0°F | +2.8°F | 0.44 in |
| 2022 | 70.9°F | +3.7°F | 1.49 in |
| 2023 | 65.3°F | −1.9°F | 0.53 in |
| 2024 | 70.0°F | +2.8°F | 0.00 in |
| 2025 | 69.0°F | +1.8°F | 0.21 in |
| 2026 | 64.6°F | −2.6°F | 0.82 in |
Source: records: ACIS, station USC00043573; recent months: ACIS, station USC00043573. Records and recent months use complete months only.
How does September in Grass Valley compare across California?
Across the 219 places PlainClimate covers in California, September normal highs run from 64°F in Eureka to 104°F in Brawley; Grass Valley's is 82°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.
Other months and places
- Grass Valley in August87°F by day, 57°F at night
- Grass Valley in October72°F by day, 44°F at night
- Grass Valley through the yearEvery month, frost dates, records and recent years
- California in SeptemberThe statewide normal and the warmest and coolest places
- Brawley: California's warmest Septembernormal high 104°F