The temperatures in Napa in September are comfortable with low of 15°C and and high up to 29°C.
You can expect up to 3 rainy days in Napa during the month of September.
Our weather forecast can give you a great sense of what weather to expect in Napa in September 2025.
If you’re planning to visit Napa in the near future, we highly recommend that you review the 14 day weather forecast for Napa before you arrive.
Temperatures
29° / 15°
Rainy Days
0
Snowy Days
0
Dry Days
30
Rainfall
3
mm
Sun Hours
11.9
Hrs