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 to 75°F, 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 to 55°F. 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 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 »
  September in Los Angeles observes a shift from the intense summer weather to the moderately warm autumn season. In Los Angeles, during September, the rain falls for 2.1 days and regularly aggregates up to 0.12" of precipitation.
• San Francisco - September »
  The month with the warmest seawater in San Francisco is September, with an average ocean temperature of 57.4°F. 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" of rain.
• San Diego - September »
  In San Diego, during September, the rain falls for 4.5 days and regularly aggregates up to 0.39" of precipitation. In September, the average ocean temperature in San Diego is 66.7°F.
• San Jose - September »
  The months with the lowest humidity in San Jose are July and September, with an average relative humidity of 60%. On the first day of September in San Jose sunrise is at 6:38 am and sunset at 7:36 pm.
• Sacramento - September »
  The least humid month in Sacramento is September, with an average relative humidity of 45%. The average high-temperature in Sacramento during September is a still hot 89.1°F, almost matching the conditions of the preceding month.
• Fresno - September »
  In Fresno, during September, the rain falls for 2.4 days and regularly aggregates up to 0.16" of precipitation. In September, in Fresno, the rain falls for 2.4 days.
• Long Beach - September »
  In Long Beach, California, in September, it is raining for 3.3 days, with typically 0.24" of accumulated precipitation. The months with the highest UV index in Long Beach, California, are June through September, with an average maximum UV index of 6.
• Oakland - September »
  The month with the warmest seawater in Oakland is September, with an average ocean temperature of 57.4°F. The month with the warmest seawater in Oakland is September, with an average ocean temperature of 57.4°F.
• Bakersfield - September »
  September in Bakersfield, California, sees a slight reduction in average high-temperature, with a shift from a sweltering 95.7°F in August to a hot 90°F. On the first day of September in Bakersfield, sunrise is at 6:28 am and sunset at 7:23 pm.
• Anaheim - September »
  In Anaheim in September, it is raining for 3.5 days, with typically 0.2" of accumulated precipitation. June through September, with an average maximum UV index of 6, are months with the highest UV index in Anaheim, California.
• Santa Ana - September »
  On the last day of September, in Santa Ana sunrise is at 6:45 am and sunset at 6:37 pm PDT. September brings a slight relief from the peak summer heat in Santa Ana, with temperatures subtly decreasing.
• Riverside - September »
  In Riverside in September, it is raining for 2.1 days, with typically 0.08" of accumulated precipitation. Riverside observes a noteworthy temperature drop from the daily highs during September nights, with a mean temperature of 64°F.