Clearlake weather in September: Clearlake, California: normal highs, lows, rain and records for September
Clearlake in September has a normal high of 85°F and a normal low of 50°F, a daily mean of 68°F, falling from 89°F on the 1st to 81°F by the 30th. Measurable precipitation falls on 1 days in a normal September, 0.17 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 30°C and low of 10°C, 4 mm of precipitation in September.
- NOAA stationClearlake (4 mi SE)
- Station IDUSC00041806
- Location38.92°N 122.57°W
- Elevation1,349 ft (411 m)
- From the center4 miles
- Population16,636
- Jan 55° 33°
- Feb 58° 34°
- Mar 62° 35°
- Apr 66° 39°
- May 73° 45°
- Jun 83° 52°
- Jul 91° 56°
- Aug 91° 54°
- Sep 85° 50°
- Oct 75° 43°
- Nov 63° 36°
- Dec 55° 33°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Clearlake in September?
The normal high is 85°F and the normal low 50°F, for a daily mean of 67.9°F. September is 4.5°F cooler than August and 8.6°F warmer than October. September is the 3rd warmest month of the year in Clearlake and the 10th wettest. Across the month the normal high falls 8°F, from 89°F on September 1 to 81°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 66°F and 70°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 5%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 89°F | 52°F | 2% | 1% |
| September 8 | 87°F | 52°F | 2% | 1% |
| September 15 | 86°F | 51°F | 2% | 1% |
| September 22 | 84°F | 49°F | 3% | 2% |
| September 30 | 81°F | 48°F | 5% | 3% |
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 | 89°F | 52°F | 2% | 1% | 13 h |
| September 2 | 88°F | 52°F | 2% | 1% | 13 h |
| September 3 | 88°F | 52°F | 2% | 1% | 13 h |
| September 4 | 88°F | 52°F | 2% | 1% | 13 h |
| September 5 | 88°F | 52°F | 2% | 1% | 12 h 50 min |
| September 6 | 88°F | 52°F | 2% | 1% | 12 h 50 min |
| September 7 | 88°F | 52°F | 2% | 1% | 12 h 50 min |
| September 8 | 87°F | 52°F | 2% | 1% | 12 h 50 min |
| September 9 | 87°F | 51°F | 2% | 1% | 12 h 50 min |
| September 10 | 87°F | 51°F | 2% | 1% | 12 h 40 min |
| September 11 | 87°F | 51°F | 2% | 1% | 12 h 40 min |
| September 12 | 87°F | 51°F | 2% | 1% | 12 h 40 min |
| September 13 | 86°F | 51°F | 2% | 1% | 12 h 40 min |
| September 14 | 86°F | 51°F | 2% | 1% | 12 h 30 min |
| September 15 | 86°F | 51°F | 2% | 1% | 12 h 30 min |
| September 16 | 86°F | 50°F | 2% | 1% | 12 h 30 min |
| September 17 | 85°F | 50°F | 3% | 1% | 12 h 30 min |
| September 18 | 85°F | 50°F | 3% | 1% | 12 h 20 min |
| September 19 | 85°F | 50°F | 3% | 2% | 12 h 20 min |
| September 20 | 85°F | 50°F | 3% | 2% | 12 h 20 min |
| September 21 | 84°F | 50°F | 3% | 2% | 12 h 20 min |
| September 22 | 84°F | 49°F | 3% | 2% | 12 h 10 min |
| September 23 | 84°F | 49°F | 4% | 2% | 12 h 10 min |
| September 24 | 83°F | 49°F | 4% | 2% | 12 h 10 min |
| September 25 | 83°F | 49°F | 4% | 2% | 12 h 10 min |
| September 26 | 83°F | 49°F | 4% | 2% | 12 h |
| September 27 | 82°F | 48°F | 4% | 3% | 12 h |
| September 28 | 82°F | 48°F | 5% | 3% | 12 h |
| September 29 | 82°F | 48°F | 5% | 3% | 12 h |
| September 30 | 81°F | 48°F | 5% | 3% | 11 h 50 min |
- Normal high
- 85°FSeptember average
- Normal low
- 50°FSeptember average
- Precipitation
- 0.17 inmonth total
- Days with precipitation
- 10.01 inch or more
- Days at 90°F or more
- 13
- Daylight
- 13 h to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 29
- Days at 80°F or more
- 24
- Sunshine
- 93%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USC00041806; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Clearlake in September?
On a given September day the chance of 0.01 inch or more is 3% on average, highest around September 30 (5%). In all, 0.17 in falls on 1 days of a normal September.
In a normal September in Clearlake, 13 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USC00041806.
What are the records for September in Clearlake?
The warmest September temperature on this station's record (since 1954) is 113°F, on September 7, 2022; the coldest is 30°F, on September 19, 1965. The wettest September brought 4.11 in (1989).
The September mean against the 1991-2020 normal of 67.9°F: 2022 70.4°F (+2.5), 2024 70.0°F (+2.1), 2025 70.0°F (+2.1), 2026 67.0°F (−0.9). 3 of 4 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2022 | 70.4°F | +2.5°F | 1.99 in |
| 2024 | 70.0°F | +2.1°F | 0.00 in |
| 2025 | 70.0°F | +2.1°F | 0.52 in |
| 2026 | 67.0°F | −0.9°F | 0.03 in |
Source: records: ACIS, station USC00041806; recent months: ACIS, station USC00041806. Records and recent months use complete months only.
How does September in Clearlake 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; Clearlake's is 85°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.
Other months and places
- Clearlake in August91°F by day, 54°F at night
- Clearlake in October75°F by day, 43°F at night
- Clearlake 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