September weather forecastSanta Rosa, CA
September
Weather in September
In Santa Rosa, September transitions from summer to fall with temperatures cooling down moderately from August. The slight increase in rainfall compared to the bone-dry summer months also nudges the weather towards fall. The steady decrease in daylight hours continues through September, indicating the passage of seasons. Wind speeds remain nearly constant while the cloud cover experiences a minor increment. The return of comparatively cooler nights outlines the changing weather conditions of Santa Rosa.Temperature
Santa Rosa transitions into September recording an average high-temperature of a still warm 79°F (26.1°C), closely aligning with the preceding month's temperature. Despite a stark disparity with daily highs, Santa Rosa records an average nighttime temperature of 54.7°F (12.6°C) in September.Humidity
With an average relative humidity of 63%, September is the least humid month.Rainfall
In Santa Rosa, in September, during 2.8 rainfall days, 0.12" (3mm) of precipitation is typically accumulated. Throughout the year, there are 72.8 rainfall days, and 12.01" (305mm) of precipitation is accumulated.Daylight
In Santa Rosa, the average length of the day in September is 12h and 25min.On the first day of the month, sunrise is at 6:41 am and sunset at 7:40 pm. On the last day of September, sunrise is at 7:06 am and sunset at 6:54 pm PDT.
Sunshine
In September, the average sunshine in Santa Rosa is 11h.UV index
In September, the average daily maximum UV index in Santa Rosa is 5. A UV Index reading of 3 to 5 represents a moderate health risk from exposure to the Sun's UV radiation for the average person.Note: In September, a daily UV index of 5 turns into the following recommendations:
Undertake protective steps - Recommendations to avoid sunburn are issued. Considering the harmful UV rays from the Sun during midday, it's essential to reduce exposure. Fend off the sun's harsh rays with appropriate clothing, a wide-brim hat, and UV-protective sunglasses.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Santa Rosa, CA
- Average high temperature in September: 79°F
The warmest month (with the highest average high temperature) is August (79.7°F).
The month with the lowest average high temperature is December (55.6°F).
- Average low temperature in September: 54.7°F
The months with the highest average low temperature are August and September (54.7°F).
The coldest month (with the lowest average low temperature) is December (41.9°F).
Average pressure in September
Santa Rosa, CA
- Average pressure in September: 29.92"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The months with the lowest atmospheric pressure are June, August and September (29.92"Hg).
Average wind speed in September
Santa Rosa, CA
- Average wind speed in September: 5.2mph
The windiest month (with the highest average wind speed) is May (7.1mph).
The calmest month (with the lowest average wind speed) is November (4.9mph).
Average humidity in September
Santa Rosa, CA
- Average humidity in September: 63%
The month with the highest relative humidity is March (77%).
The month with the lowest relative humidity is September (63%).
Average rainfall in September
Santa Rosa, CA
- Average rainfall in September: 0.12"
The wettest month (with the highest rainfall) is February (2.64").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in September
Santa Rosa, CA
- Average rainfall days in September: 2.8 days
The month with the highest number of rainy days is March (12.6 days).
The month with the least rainy days is August (0.8 days).
Average daylight in September /
Average sunshine in September
Santa Rosa, CA
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 48min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in September: 11h and 0min
The month with the most sunshine is July (Average sunshine: 11h and 54min).
The month with the least sunshine is December (Average sunshine: 5h and 42min).
Average sunshine days in September
Santa Rosa, CA
- Average sunshine days in September: 26.5 days
The month with the most sunshine days is July (27.2 days).
The month with the least sunshine days is March (17.1 days).
Average UV index in September
Santa Rosa, CA
- Average UV index in September: 5
The month with the highest UV index is June (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 3).
Average cloud cover in September
Santa Rosa, CA
- Average cloud cover in September: 10
The month with the most cloud cover is March (Cloud cover 39).
The month with the least cloud cover is July (Cloud cover 9).
Average visibility in September
Santa Rosa, CA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
