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Napa September Weather

Averages and records for weather in Napa, California in the month of September.

Typical Napa September Weather 1991–2020
Average daily high	80.9 °F
Average daily low	50.8 °F
Average monthly precipitation	0.1 inches
Daily chance of precipitation	2.9%

Napa September Weather Records 1901–2024
Highest temperature	115 °F	September 6, 2022
Lowest temperature	35 °F	September 29, 2019
Highest daily low	72 °F	September 17, 1923
Lowest daily high	58 °F	September 30, 1930
Hottest average high temperature	89.8 °F	1984
Coldest average high temperature	71.8 °F	1925
Most daily precipitation	2.0 inches	September 23, 1904
Most monthly precipitation	4.8 inches	1904

Note: Daily averages are a moving average which includes 14 days before and after

Day	Average (°F)		Record (°F)
Day	High	Low	High	Low
September 1	80.7	52.7	107	44
September 2	80.7	52.6	109	41
September 3	80.8	52.4	105	40
September 4	81.0	52.3	105	42
September 5	81.0	52.1	111	42
September 6	81.1	52.0	115	42
September 7	81.1	51.9	110	39
September 8	81.1	51.7	108	42
September 9	81.1	51.5	109	40
September 10	81.2	51.4	105	39
September 11	81.2	51.3	107	40
September 12	81.1	51.3	107	40
September 13	81.1	51.1	107	39
September 14	81.1	51.0	108	40
September 15	81.0	50.9	106	39
September 16	80.9	50.7	104	38
September 17	80.7	50.6	102	42
September 18	80.5	50.5	103	38
September 19	80.4	50.3	104	37
September 20	80.1	50.2	105	38
September 21	79.9	50.1	105	41
September 22	79.7	49.9	105	36
September 23	79.7	49.7	106	39
September 24	79.7	49.5	104	39
September 25	79.7	49.4	101	37
September 26	79.5	49.2	105	38
September 27	79.3	49.0	101	40
September 28	79.3	48.8	103	40
September 29	79.4	48.6	101	35
September 30	79.5	48.5	100	37

Weather Station Details

Years	Station	Coordinates
1999–2024	Napa County Airport	location
1901–1998	Napa State Hospital	location