Santa Rosa, CA weather in September
September in Santa Rosa: warm and dry. Highs 84°F, lows 48°F, about 2 wet days. This is the peak of the warm season in Santa Rosa. A good month for most outdoor plans.
- Normal high
- 84°F
- Normal low
- 48°F
- Wet days
- 2
- 0.2 in total
- Muggy days
- 0
- dew point 65°F+
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 85°F | 82°F |
| Normal low | 49°F | 47°F |
| Chance of a wet day | 4% | 8% |
| Sunrise / sunset | 6:40 am / 7:41 pm | 7:05 am / 6:55 pm |
| Daylight | 13.0 h | 11.8 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Pacific Time).
A typical September day
- 6 am57°Fdew point 51°F
- 9 am70°Fdew point 51°F
- Noon81°Fdew point 50°F
- 3 pm85°Fdew point 48°F
- 6 pm76°Fdew point 50°F
- 9 pm65°Fdew point 51°F
NOAA hourly normals (local standard time) from Travis AFB (44 mi away); average wind 14 mph; clear or few clouds in 87% of daytime hours, mostly cloudy or overcast in 7%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F9 of 30
- Hot dayshigh 90°F or more8 of 30
- Muggy daysdaily mean dew point 65°F or more0 of 30
- Wet daysat least 0.01 in of rain or melted snow2 of 30
- Notable rainat least 0.10 in1 of 30
- Freezing nightslow 32°F or below0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain in September
Normal precipitation is 0.2 in; a dry September brings about 0.0 in and a wet one about 0.2 in (25th and 75th percentiles). Days with half an inch or more are rare.
How September varies from year to year
- Warmest September, 1991-20202017: average high 90°F
- Coolest September1999: average high 79°F
- Wettest September2014: 1.0 in
- Driest September1992: no measurable precipitation
- Highest reading114°F (September 6, 2020)
- Lowest reading28°F (September 20, 2012)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 84°F | 84°F | 78°F |
| Normal low | 50°F | 48°F | 44°F |
| Wet days | 1 | 2 | 4 |
| Comfortable days | 11 | 9 | 15 |
| Daylight | 13.6 h | 12.4 h | 11.2 h |
Highs change by 0°F from August and -6°F into October.
Nearby alternatives in September
- Warmer: Sacramento, CA67 mi · high 89°F · 1 wet day
- Cooler: San Francisco, CA49 mi · high 70°F · 1 wet day
How Santa Rosa ranks in September
- Normal high156th warmest of 378 cities; 38th of 60 in California
- Wet days56th driest of 378
- Comfortable days165th most of 342
What to pack for Santa Rosa in September
- Layers – afternoons near 84°F but nights near 48°F
Heating and cooling
September has 43 heating degree days and 69 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Santa Rosa in September?
The normal high is 84°F and the normal low is 48°F. From 1991 to 2020 the hottest September reading was 114°F (September 6, 2020).
Does it rain a lot in Santa Rosa in September?
About 2 days in September have at least 0.01 in of precipitation, and the normal total is 0.2 in. The wettest September in 1991-2020 was in 2014 (1.0 in); the driest was in 1992, with no measurable precipitation.
Is September a good time to visit Santa Rosa?
September ranks 9th of 12 months on our comfort score for Santa Rosa (60 out of 100). It has about 9 comfortable days and about 8 days at 90°F or hotter. The best months are April and May.
Where the numbers come from
- Temperature and rain: Graton (USC00043578), 8.2 mi W of the city center, 200 ft . NOAA normals and daily records, 1991-2020.
- Snowfall, snow depth and frost dates: Santa Rosa (USC00047965), 1.1 mi N of the city center, 166 ft . NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour and cloud cover: Travis AFB (USW00023202), 44 mi ESE of the city center, 59 ft (106 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Sonoma County Airport (724957-23213), 6.8 mi NW of the city center, 119 ft . Hourly observations, 1991-2020.