Half Moon Bay Weather in September

What's the weather like in Half Moon Bay (California) in September 2025?

The climate in Half Moon Bay during September can be summarized as mild and very dry.

September is in the fall / autumn in Half Moon Bay and is typically the warmest month of the year. Daytime maximum temperatures average around 23°C (73°F), whilst at night 12°C (53°F) is normal.

Half Moon Bay weather averages (imperial / metric)
Daytime temperature 22.8°C 73°F
Nightly temperature 11.9°C 53.3°F
Average temperature 17.3°C 63.1°F
Daily sunshine 9.9 hrs
Avg rainfall 7 mm 0.3 ins
Rainy days 2 days
Sea temperature 14.4°C 57.9°F
Humidity 71%
Windspeed 16.6kph 10 mph

On average September is the 4th driest month of the year in Half Moon Bay with around 7mm 0.3 inches of rain making it a very dry time to visit.

On the flip side this corresponds to an average of 9.9 hours of sunshine per day.

September temperatures in Half Moon Bay

Half Moon Bay average temperature in September

September rainfall

Half Moon Bay average rain in September

September hourly sunshine

Half Moon Bay average rain in September

The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Half Moon Bay in September 2025.

Other monthly averages

Best places to visit in September

UV index Best time to go?

Beta

Current (hourly) weather 15 day forecast

Half Moon Bay weather stats

Half Moon Bay weather statistics
Hottest month: September 22.5°C 72.5°F
Driest month: July 2mm 0.1ins
Sunniest month: April 11hrs
Coldest month: January 13.4°C 56.1°F
Wettest month: January 146mm 5.7ins
Map showing location of Half Moon Bay (37.46355, -122.42859) Half Moon Bay map pin © Google

Locations nearby

Top United States locations