Climateby Month

Napa, CA climate by month

NOAA 1991-2020 normals · 19 ft elevation

Highs in Napa peak at 84°F in September (warm) and bottom out at 59°F in December (cool). The wettest month is January (about 12 wet days) and the driest is July (about 0). Snow is rare. By our comfort score the best month is May.

Warmest month
84°F
September normal high
Coldest month
40°F
December normal low
Wet days a year
68
26.7 in of precipitation
Muggy days a year
0
dew point 65°F or higher

How warm is Napa?

Normal highs range from 59°F in December to 84°F in September.

40°50°60°70°80°90° January: normal high 59°F (15°C), low 40°F (4°C) 59° 40° February: normal high 63°F (17°C), low 42°F (6°C) March: normal high 68°F (20°C), low 44°F (7°C) April: normal high 72°F (22°C), low 46°F (8°C) May: normal high 77°F (25°C), low 50°F (10°C) June: normal high 82°F (28°C), low 54°F (12°C) July: normal high 83°F (28°C), low 56°F (13°C) August: normal high 84°F (29°C), low 56°F (13°C) 84° 56° September: normal high 84°F (29°C), low 53°F (12°C) October: normal high 78°F (26°C), low 49°F (9°C) November: normal high 66°F (19°C), low 44°F (7°C) December: normal high 59°F (15°C), low 40°F (4°C) JFMAMJJASOND

Bars run from the normal low to the normal high for each month.

How rainy is Napa?

January has the most wet days (about 12); the year brings about 27 in of precipitation.

January: 12 wet days 12 February: 11 wet days March: 10 wet days April: 7 wet days May: 4 wet days June: 1 wet days July: 0 wet days 0 August: 0 wet days September: 1 wet days October: 4 wet days November: 8 wet days December: 12 wet days JFMAMJJASOND

Wet day: at least 0.01 in of rain or melted snow, counted from daily records 1991-2020.

How humid is Napa?

Muggy days (dew point 65°F or higher) are rare in any month.

January: 0 muggy days 0 February: 0 muggy days March: 0 muggy days April: 0 muggy days May: 0 muggy days June: 0 muggy days July: 0 muggy days August: 0 muggy days September: 0 muggy days October: 0 muggy days November: 0 muggy days December: 0 muggy days JFMAMJJASOND

Muggy day: daily mean dew point of 65°F or higher, from hourly observations 1991-2020 at Napa County Airport, 6.2 mi S of the city center.

How much daylight?

Daylight ranges from about 9.6 hours in December to 14.8 hours in June.

January: 9.8 hours of daylight February: 10.8 hours of daylight March: 12.0 hours of daylight April: 13.2 hours of daylight May: 14.3 hours of daylight June: 14.8 hours of daylight 14.8 July: 14.5 hours of daylight August: 13.6 hours of daylight September: 12.4 hours of daylight October: 11.2 hours of daylight November: 10.1 hours of daylight December: 9.6 hours of daylight 9.6 JFMAMJJASOND
See all numbers
Monthly climate normals and day counts for Napa, 1991-2020
MonthHighLowPrecip.Wet daysMuggy daysDaylight
January 59°F40°F 5.0 in12 0 9.8 h
February 63°F42°F 5.1 in11 0 10.8 h
March 68°F44°F 3.7 in10 0 12.0 h
April 72°F46°F 1.7 in7 0 13.2 h
May 77°F50°F 1.1 in4 0 14.3 h
June 82°F54°F 0.3 in1 0 14.8 h
July 83°F56°F 0.0 in0 0 14.5 h
August 84°F56°F 0.06 in0 0 13.6 h
September 84°F53°F 0.09 in1 0 12.4 h
October 78°F49°F 1.3 in4 0 11.2 h
November 66°F44°F 2.8 in8 0 10.1 h
December 59°F40°F 5.5 in12 0 9.6 h

High and low: NOAA 1991-2020 normal daily high and low. Wet days: at least 0.01 in of rain or melted snow. Muggy days: daily mean dew point 65°F or higher.

Best months to visit Napa

By our comfort score, the best month is May.

Comfort score by month (0-100) and its parts, in days per month
MonthScoreComfortableNotable rainHot or cold
Jan 46590
Feb 591280
Mar 691870
Apr 771941
May 812123
Jun 731316
Jul 721306
Aug 691306
Sep 621108
Oct 691723
Nov 661650
Dec 44380

Score = 40 × share of comfortable days + 25 × share of days without notable rain + 20 × share of days neither hot (90°F+) nor cold (high 40°F or below) + 15 × daylight. How the score works.

Frost dates in Napa

The last spring frost typically comes around Feb 12, and the first fall frost around Dec 4, leaving 299 frost-free days in a typical year.

Frost and freeze dates for Napa
Typical date1 year in 10
Last spring frost (32°F)Feb 12after Mar 13
First fall frost (32°F)Dec 4before Nov 15
Last hard freeze (28°F)Jan 11after Feb 13
First hard freeze (28°F)Dec 19before Dec 1
Frost-free season299 daysunder 257 days

"Typical" is the date with a 50% chance of a later spring frost (or earlier fall frost). Planting after the "1 year in 10" spring date gives a 90% chance of no further frost. The Old Farmer's Almanac publishes 30% dates, which fall between our typical and 1-in-10 dates.

Station: Napa State Hospital (USC00046074), NOAA 1991-2020 freeze probabilities. Frost dates for every city in California.

Hottest and coldest readings, 1991-2020

The highest reading was 111°F (September 7, 2020); the lowest was 22°F (December 22, 1998).

From the temperature station's daily records with NOAA quality flags removed. Not an all-time record.

Near Napa

Similar climates elsewhere

Where the numbers come from

  • Temperature, rain, snowfall and frost dates: Napa State Hospital (USC00046074), 1.8 mi SE of the city center, 35 ft . NOAA normals and daily records, 1991-2020.
  • Snow depth: Fairfield (USC00042934), 12 mi E of the city center, 40 ft . NOAA normals and daily records, 1991-2020.
  • Humidity and wind by hour and cloud cover: Travis AFB (USW00023202), 19 mi E of the city center, 59 ft . NOAA normals and daily records, 1991-2020.
  • Daily humidity and wind: Napa County Airport (724955-93227), 6.2 mi S of the city center, 15 ft . Hourly observations, 1991-2020.

Distances from the city center (USGS). Methodology · Report an error