Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
September is the warmest month, with the temperature often reaching an average high of 70.2°F (21.2°C) and an average low of 56.8°F (13.8°C).Humidity
The average relative humidity in September is 73%.Rainfall
In Millbrae, in September, it is raining for 3.4 days, with typically 0.16" (4mm) of accumulated precipitation. Throughout the year, there are 81.5 rainfall days, and 12.8" (325mm) of precipitation is accumulated.Daylight
In Millbrae, the average length of the day in September is 12h and 25min.On the first day of September, sunrise is at 6:40 am and sunset at 7:38 pm. On the last day of the month, sunrise is at 7:04 am and sunset at 6:53 pm PDT.
Sunshine
In September, the average sunshine is 10.9h.UV index
June through September, with an average maximum UV index of 5, are months with the highest UV index. A UV Index value of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV rays for the average person.Note: The maximum daily UV index of 5 in September converts into the following recommendations:
Undertake protective steps - Obligation to safeguard skin and eyes from harm is in place. The Sun's harshest UV rays are around midday; it's wise to seek shade and limit time outdoors. A wide-brimmed hat is a shield, deflecting up to 50% of harmful UV radiation from eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the warmest month?
What are the temperatures in September?
What is the average humidity in September?
How many days does it rain in September?
What is the average length of the day in September?
What time are sunrise and sunset in September in Millbrae?
How long on average sun shines in September?
When is the highest UV index?
What is the UV index reading in September?
Average temperature in September
Millbrae, CA
- Average high temperature in September: 70.2°F
The warmest month (with the highest average high temperature) is September (70.2°F).
The month with the lowest average high temperature is December (55.6°F).
- Average low temperature in September: 56.8°F
The month with the highest average low temperature is September (56.8°F).
The coldest month (with the lowest average low temperature) is January (47.5°F).
Average pressure in September
Millbrae, CA
- Average pressure in September: 29.92"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is September (29.92"Hg).
Average wind speed in September
Millbrae, CA
- Average wind speed in September: 6.1mph
The windiest month (with the highest average wind speed) is April (8.3mph).
The calmest month (with the lowest average wind speed) is September (6.1mph).
Average humidity in September
Millbrae, CA
- Average humidity in September: 73%
The month with the highest relative humidity is August (78%).
The month with the lowest relative humidity is October (70%).
Average rainfall in September
Millbrae, CA
- Average rainfall in September: 0.16"
The wettest month (with the highest rainfall) is February (2.44").
The driest month (with the least rainfall) is July (0.08").
Average rainfall days in September
Millbrae, CA
- Average rainfall days in September: 3.4 days
The month with the highest number of rainy days is March (12.8 days).
The months with the least rainy days are June and July (2.4 days).
Average daylight in September /
Average sunshine in September
Millbrae, CA
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in September: 10h and 5min
The month with the most sunshine is July (Average sunshine: 11h and 48min).
The month with the least sunshine is December (Average sunshine: 5h and 48min).
Average sunshine days in September
Millbrae, CA
- Average sunshine days in September: 23.2 days
The month with the most sunshine days is July (24.6 days).
The month with the least sunshine days is March (16.3 days).
Average UV index in September
Millbrae, CA
- Average UV index in September: 5
The months with the highest UV index are June, July, August and September (UV index 5).
The months with the lowest UV index are February and December (UV index 3).
Average cloud cover in September
Millbrae, CA
- Average cloud cover in September: 15
The month with the most cloud cover is March (Cloud cover 36).
The months with the least cloud cover are July and September (Cloud cover 15).
Average visibility in September
Millbrae, 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).
Millbrae, California, USA
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