September weather forecast
California, USA

September marks the transition from summer to autumn in California, with weather changes that vary across the state. It's a month of mixed conditions, retaining some summer characteristics while beginning to show signs of the coming fall.

In coastal regions such as San Francisco and Los Angeles, temperatures generally range from 65°F (18.3°C) to 75°F (23.9°C), remaining pleasant but starting to cool down slightly from the peak summer months.

Inland areas and the Sierra Nevada mountains experience temperatures between 45°F (7.2°C) to 55°F (12.8°C). The weather is still warm, but the cooler evenings and nights signal the onset of autumn.

Desert regions like Death Valley continue to be hot but see a more pronounced decrease in temperatures compared to August. Though temperatures above 90°F (32.2°C) are common, the extreme heat of mid-summer begins to wane.

September brings a slight increase in precipitation in some parts of the state, particularly in the north. Though still minimal, the rainfall hints at the wetter winter months to come.

Comparing September to August, the weather in most regions of California begins to cool slightly, signaling the end of summer and the beginning of autumn. The coastal areas continue to benefit from the moderating influence of the Pacific Ocean, while inland and desert areas experience more noticeable changes. September's weather is characterized by a blend of summer warmth and the first hints of autumn coolness, creating a diverse and transitional climate across the state. The shift in temperatures, along with a slight increase in precipitation in some areas, marks September as a month of change in California's weather landscape.

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• Los Angeles - September »
  In Los Angeles during September, the rain falls for 2.1 days and regularly aggregates up to 0.12" (3mm) of precipitation. September in Los Angeles observes a shift from the intense summer weather to the moderately warm autumn season.
• San Francisco - September »
  With an average ocean temperature of 57.4°F (14.1°C), September is the month with the warmest seawater in San Francisco. July through September are months with the least rain in San Francisco when the rain falls for 2.5 days and typically aggregates up to 0.08" (2mm) of rain.
• San Diego - September »
  On the first day of September in San Diego sunrise is at 6:23 am and sunset at 7:12 pm. In San Diego in September, it is raining for 4.5 days, with typically 0.39" (10mm) of accumulated precipitation.
• San Jose - September »
  July and September, with an average relative humidity of 60%, are the least humid months in San Jose, California. As August transitions into September, the average high-temperature in San Jose rests at a still moderately hot 79.7°F (26.5°C), maintaining a close resemblance to the previous month.
• Sacramento - September »
  September is the least humid month with an average relative humidity of 45%. On the first day of September in Sacramento, sunrise is at 6:35 am and sunset at 7:35 pm.
• Fresno - September »
  On the first day of September in Fresno sunrise is at 6:30 am and sunset at 7:26 pm. Fresno's September weather features a light decline in high-temperatures, reducing from a torrid 98.2°F (36.8°C) in August to a tropical 91.8°F (33.2°C).
• Long Beach - September »
  On the first day of September in Long Beach sunrise is at 6:27 am and sunset at 7:17 pm. On the first day of September in Long Beach, sunrise is at 6:27 am and sunset at 7:17 pm.
• Oakland - September »
  With an average ocean temperature of 57.4°F (14.1°C), September is the month with the warmest seawater in Oakland. In Oakland, September is the warmest month, with temperatures averaging a high of 73.9°F (23.3°C) and a low of 56.5°F (13.6°C).
• Bakersfield - September »
  On the first day of September in Bakersfield sunrise is at 6:29 am and sunset at 7:22 pm. In Bakersfield during September, the rain falls for 1.6 days and regularly aggregates up to 0.08" (2mm) of precipitation.
• Anaheim - September »
  The advent of September in Anaheim brings an average high-temperature of a still moderately hot 82.2°F (27.9°C), exhibiting minor difference from the previous month. On the first day of September in Anaheim, sunrise is at 6:25 am and sunset at 7:16 pm.
• Santa Ana - September »
  June through September, with an average maximum UV index of 6, are months with the highest UV index in Santa Ana, California. September brings a slight relief from the peak summer heat in Santa Ana, with temperatures subtly decreasing.
• Riverside - September »
  On the first day of September in Riverside sunrise is at 6:23 am and sunset at 7:14 pm. In Riverside, California, in September, during 2.1 rainfall days, 0.08" (2mm) of precipitation is typically accumulated.