Napa weather in September 2025

Expect daytime maximum temperatures of 27°C in Napa, California in September based on long-term weather averages. There are 10 hours of sunshine per day on average.

  • 27°C maximum daytime temperature in September in Napa27
    27°C max day temperature
  • 10 hours of sunshine per day
  • 2 days with some rainfall in September in Napa2
    2 days with some rainfall
  • 11°C minimum night-time temperature in September in Napa11
    11°C min night temperature
  • 12 hours of daylight per day in September in Napa12
    12 hours of daylight per day
  • Moderate heat & humidity in September in NapaM
    Moderate heat & humidity
  • 10 mm monthly rainfall in September in Napa10
    10 mm of monthly rainfall
  • UV (maximum) index 7 (High) in September in Napa7
    7 (High) UV index

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The September weather guide for California (Napa) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C / mm)  |  Imperial (°F / inches)

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How hot is it in Napa in September?

Daytime temperatures usually reach 27°C in Napa in September with moderate heat and humidity, falling to 11°C at night.

How sunny is it in Napa in September?

There are normally 10 hours of bright sunshine each day in Napa in September - that's 80% of daylight hours.

Does it ever rain in Napa in September?

There are usually 2 days with some rain in Napa in September and the average monthly rainfall is 10mm.

Napa September sunrise & sunset times

Browse the sunrise and sunset times for Napa in September 2025. Select a month to view Napa sunrise and sunset times for the next 12 months.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 05:39 18:38
Monday, 15th September 2025 05:51 18:16
Tuesday, 30th September 2025 06:04 17:53

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