September weather forecastHalf Moon Bay, CA
September
Weather in September
September, the first month of the autumn in Half Moon Bay, is still a comfortable month, with an average temperature fluctuating between 56.7°F (13.7°C) and 66.9°F (19.4°C).Temperature
Half Moon Bay's September weather reaches an average high of 66.9°F (19.4°C) and an average low of 56.7°F (13.7°C), making it the warmest month.Humidity
In Half Moon Bay, the average relative humidity in September is 77%.Rainfall
In September, the rain falls for 3.6 days. Throughout September, 0.16" (4mm) of precipitation is accumulated. Throughout the year, there are 76.8 rainfall days, and 8.54" (217mm) of precipitation is accumulated.Daylight
In September, the average length of the day is 12h and 25min.On the first day of the month, sunrise is at 6:40 am and sunset at 7:38 pm. On the last day of September, sunrise is at 7:05 am and sunset at 6:53 pm PDT.
Sunshine
The average sunshine in September is 10.7h.UV index
The months with the highest UV index are June, August and September, with an average maximum UV index of 5. A UV Index value of 3 to 5 symbolizes a medium health hazard from exposure to the Sun's UV radiation for the average person.Note: A maximum UV index of 5 in September translates into the following recommendations:
Undertake protective steps - Obligation to safeguard skin and eyes from harm is in place. Considering the strength of solar radiation at midday, one should avoid direct Sun exposure. By wearing a generously brimmed hat, you can cut UV radiation exposure significantly.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Half Moon Bay, CA
- Average high temperature in September: 66.9°F
The warmest month (with the highest average high temperature) is September (66.9°F).
The month with the lowest average high temperature is December (55.6°F).
- Average low temperature in September: 56.7°F
The month with the highest average low temperature is September (56.7°F).
The coldest month (with the lowest average low temperature) is February (48.7°F).
Average pressure in September
Half Moon Bay, 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
Half Moon Bay, CA
- Average wind speed in September: 7mph
The windiest month (with the highest average wind speed) is April (9.6mph).
The calmest month (with the lowest average wind speed) is August (6.6mph).
Average humidity in September
Half Moon Bay, CA
- Average humidity in September: 77%
The month with the highest relative humidity is August (82%).
The months with the lowest relative humidity are November and December (72%).
Average rainfall in September
Half Moon Bay, CA
- Average rainfall in September: 0.16"
The wettest month (with the highest rainfall) is February (1.61").
The driest months (with the least rainfall) are June and July (0.12").
Average rainfall days in September
Half Moon Bay, CA
- Average rainfall days in September: 3.6 days
The month with the highest number of rainy days is March (10.8 days).
The month with the least rainy days is June (3 days).
Average daylight in September /
Average sunshine in September
Half Moon Bay, CA
- Average daylight in September: 12h and 24min
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 42min
The month with the most sunshine is July (Average sunshine: 11h and 24min).
The month with the least sunshine is December (Average sunshine: 5h and 42min).
Average sunshine days in September
Half Moon Bay, CA
- Average sunshine days in September: 22.6 days
The month with the most sunshine days is October (24.6 days).
The months with the least sunshine days are March and August (18.8 days).
Average UV index in September
Half Moon Bay, CA
- Average UV index in September: 5
The months with the highest UV index are June, August and September (UV index 5).
The months with the lowest UV index are January, February, March, April, May, July, October, November and December (UV index 4).
Average cloud cover in September
Half Moon Bay, CA
- Average cloud cover in September: 18
The month with the most cloud cover is March (Cloud cover 38).
The month with the least cloud cover is September (Cloud cover 18).
Average visibility in September
Half Moon Bay, 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).
