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 »
  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" (3mm) of precipitation.
• San Francisco - September »
  September is the month with the warmest seawater in San Francisco with an average ocean temperature of 57.4°F (14.1°C). The months with the least rainfall in San Francisco are July through September Rain falls for 2.5 days and accumulates 0.08" (2mm) of rain.
• San Diego - September »
  In San Diego, during September, the rain falls for 4.5 days and regularly aggregates up to 0.39" (10mm) of precipitation. In September, in San Diego, California, the rain falls for 4.5 days.
• San Jose - September »
  July and September, with an average relative humidity of 60%, are the least humid months in San Jose, California. In San Jose during September, the rain falls for 2.1 days and regularly aggregates up to 0.08" (2mm) of precipitation.
• Sacramento - September »
  In Sacramento in September, it is raining for 1.9 days, with typically 0.12" (3mm) of accumulated precipitation. The average heat index, which represents the influence of relative humidity on air temperature, in September is appraised at 91.4°F (33°C).
• Fresno - September »
  On the first day of September in Fresno, sunrise is at 6:30 am and sunset at 7:27 pm. In Fresno, during September, the rain falls for 2.4 days and regularly aggregates up to 0.16" (4mm) of precipitation.
• Long Beach - September »
  Long Beach transitions into September recording an average high-temperature of a still moderately hot 78.8°F (26°C), closely aligning with the preceding month's temperature. In Long Beach during September, the rain falls for 3.3 days and regularly aggregates up to 0.24" (6mm) of precipitation.
• Oakland - September »
  The month with the warmest seawater in Oakland is September, with an average ocean temperature of 57.4°F (14.1°C). The month with the warmest seawater in Oakland is September, with an average ocean temperature of 57.4°F (14.1°C).
• Bakersfield - September »
  In Bakersfield during September, the rain falls for 1.6 days and regularly aggregates up to 0.08" (2mm) of precipitation. On the first day of September in Bakersfield, sunrise is at 6:28 am and sunset at 7:23 pm.
• Anaheim - September »
  The months with the highest UV index in Anaheim are June through September, with an average maximum UV index of 6. As Anaheim steps into September, the average high-temperature holds at a still moderately hot 82.2°F (27.9°C), hinting at a minor fluctuation from the prior month.
• 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 »
  On the last day of September, in Riverside sunrise is at 6:43 am and sunset at 6:35 pm PDT. During the nights in September, Riverside records a pronounced shift from the daytime warmth, with a consistent average temperature of 64°F (17.8°C).