Napa, California climate: Normal weather by month, frost dates and records
Napa's normal year runs from 38°F December nights to 80°F August afternoons, with 20.2 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 14.3°C, December lows of 3°C, August highs of 27°C, 514 mm of precipitation a year.
- NOAA stationNapa County Airport
- Station IDUSW00093227
- Location38.21°N 122.28°W
- Elevation14 ft (4 m)
- Population76,921
On October 14, the normal high in Napa is 76°F and the normal low 46°F, and the chance of measurable rain or snow is 10%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Napa.
- Jan 57° 38°
- Feb 61° 40°
- Mar 64° 42°
- Apr 68° 44°
- May 73° 48°
- Jun 78° 52°
- Jul 79° 55°
- Aug 80° 54°
- Sep 80° 51°
- Oct 75° 46°
- Nov 65° 40°
- Dec 57° 38°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Napa each month?
August is the warmest month, with normal highs of 80°F; December the coldest, with normal lows of 38°F. The most precipitation falls in January (4.17 in), the least in July (0.01 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 57°F | 38°F | 47.6°F | 4.17 | 10 | <1 | 9 | 9 h 50 min |
| February | 61°F | 40°F | 50.4°F | 3.95 | 10 | <1 | 5 | 10 h 50 min |
| March | 64°F | 42°F | 53.0°F | 3.01 | 10 | <1 | 2 | 11 h 50 min |
| April | 68°F | 44°F | 55.8°F | 1.26 | 6 | <1 | 1 | 13 h 10 min |
| May | 73°F | 48°F | 60.5°F | 0.80 | 3 | 1 | <1 | 14 h 10 min |
| June | 78°F | 52°F | 65.1°F | 0.22 | 1 | 3 | <1 | 14 h 50 min |
| July | 79°F | 55°F | 66.7°F | 0.01 | <1 | 2 | <1 | 14 h 40 min |
| August | 80°F | 54°F | 67.2°F | 0.02 | <1 | 3 | <1 | 13 h 40 min |
| September | 80°F | 51°F | 65.7°F | 0.07 | 1 | 5 | <1 | 12 h 30 min |
| October | 75°F | 46°F | 60.6°F | 0.93 | 3 | 2 | <1 | 11 h 20 min |
| November | 65°F | 40°F | 52.7°F | 1.97 | 7 | <1 | 5 | 10 h 10 min |
| December | 57°F | 38°F | 47.5°F | 3.82 | 10 | <1 | 11 | 9 h 30 min |
| Year (annual) | 70°F | 46°F | 57.7°F | 20.23 | 61 | 16 | 34 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 14°C | 3°C | 8.7°C | 106 mm |
| February | 16°C | 4°C | 10.2°C | 100 mm |
| March | 18°C | 5°C | 11.7°C | 76 mm |
| April | 20°C | 6°C | 13.2°C | 32 mm |
| May | 23°C | 9°C | 15.8°C | 20 mm |
| June | 26°C | 11°C | 18.4°C | 6 mm |
| July | 26°C | 13°C | 19.3°C | 0 mm |
| August | 27°C | 12°C | 19.6°C | 1 mm |
| September | 27°C | 11°C | 18.7°C | 2 mm |
| October | 24°C | 8°C | 15.9°C | 24 mm |
| November | 18°C | 5°C | 11.5°C | 50 mm |
| December | 14°C | 3°C | 8.6°C | 97 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. Napa's own co-op station Napa State Hospital does: 0 inches of snow in a normal year (see the other stations below).
Source: NOAA NCEI 1991-2020 monthly normals, station USW00093227; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Napa?
Normal highs sit between 65°F and 85°F in April, May, June, July, August, September, October and November. Of those, July has the fewest days with rain (0).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00093227.
When is the last frost in Napa?
In Napa, the last spring frost (32°F) comes after March 5 in half of years and after April 16 in one year in ten; the first autumn frost comes before November 21 in half of years and before November 3 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- March 51 year in 10 after April 16; 9 in 10 after January 26
- First autumn frost, half of years before
- November 211 year in 10 before November 3; 9 in 10 before December 13
NOAA puts the median frost-free season at 256 days, and the season without a hard freeze (28°F) at 323 days.
A hard freeze (28°F) comes after January 23 in half of springs and before December 5 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Napa in zone 9b in ZIP code 94559. By the map's own method, the average of each year's coldest night over 1991-2020, Napa's NOAA station is in zone 9a: the coldest night of a typical year reaches 22°F (22 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in California · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00093227; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Napa?
In a normal year in Napa, 16 days a year reach 90°F (2 of them 100°F or more), 34 nights fall to 32°F or colder and 61 days bring measurable precipitation.
- Days at 90°F or more
- 16a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 34a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 61a normal year
The highest temperature in this station's record (since 1998) is 115°F, on September 6, 2022; the lowest is 16°F, on December 5, 2013.
The wettest calendar year on that record is 2017, with 31.21 in.
Source: NOAA NCEI 1991-2020 annual normals, station USW00093227; records: ACIS (NOAA Regional Climate Centers), station USW00093227. Records use complete months only; a month missing more than three days is left out.
How sunny is Napa?
Over a year 87% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Napa, 5.1 kWh per square metre a day. July is the sunniest month (95%) and December the cloudiest (72%). Among the 459 U.S. places of 50,000 or more, that ranks tied 58th (with 22 others) in sunshine.
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 74% | 2.3 |
| February | 77% | 3.3 |
| March | 78% | 4.6 |
| April | 84% | 6.1 |
| May | 88% | 7.3 |
| June | 93% | 8.1 |
| July | 95% | 8.0 |
| August | 94% | 7.1 |
| September | 93% | 5.8 |
| October | 88% | 4.2 |
| November | 81% | 2.8 |
| December | 72% | 2.0 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Napa need?
A normal year in Napa brings 2,956 heating degree days, 45% fewer than the median U.S. place (5,373), and 315 cooling degree days, 65% fewer than the median (908). Five months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,153 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 541 | 0 |
| February | 407 | 0 |
| March | 374 | 0 |
| April | 279 | 3 |
| May | 157 | 16 |
| June | 52 | 53 |
| July | 19 | 74 |
| August | 15 | 84 |
| September | 47 | 66 |
| October | 154 | 19 |
| November | 368 | 1 |
| December | 544 | 0 |
| Year (annual) | 2,956 | 315 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00093227. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Napa been warmer than normal lately?
2025 averaged 57.7°F, equal to the 1991-2020 normal of 57.7°F. 3 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 57.7°F | at normal | 20.48 |
| 2022 | 58.0°F | +0.3°F | 11.91 |
| 2023 | 58.4°F | +0.7°F | 27.25 |
| 2024 | 58.6°F | +0.9°F | 24.16 |
| 2025 | 57.7°F | at normal | 15.75 |
Source: observed years: ACIS, station USW00093227. A year counts only with all twelve months complete.
How does Napa's climate compare?
Napa is warmer than 56 of the other 218 places with their own NOAA record in California, and wetter than 137. Across the 7,247 U.S. stations with normals, its annual mean of 57.7°F is warmer than 68%.
In the Köppen classification computed from these normals, Napa is Csb: temperate, dry-summer, warm summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Napa share this climate record?
American Canyon has no NOAA station with 1991-2020 normals of its own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- American Canyon, CA21,742 people · 3 mi SE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Napa's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Napa. This page uses Napa County Airport; the other differs by site and elevation, and the linked ones have pages of their own:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Napa State Hospital USC00046074 | 5 mi N | 35 ft | 60.3°F | 40°F | 83°F | 26.7 | 0 | February 12 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Napa's climate
What is the coldest month in Napa?
December, with a normal high of 57°F and a normal low of 38°F. The warmest is August (80°F by day, 54°F at night).
Does it snow in Napa?
Rarely. NOAA publishes no 1991-2020 snowfall normal for Napa's NOAA station; Napa's own co-op station Napa State Hospital records 0 inches of snow in a normal year.
What is the rainiest month in Napa?
January, with 4.17 in of precipitation in a normal year; the driest is July with 0.01 in.
What plant hardiness zone is Napa in?
The USDA's 2023 map puts Napa in zone 9b in ZIP code 94559. By the same method at Napa's NOAA station, the coldest night of a typical year reaches 22°F (22 years, 1991-2020): zone 9a.
How late can frost come in Napa?
In half of years the last 32°F night comes after March 5; in one year in ten it comes after April 16. Waiting until April 16 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Napa in OctoberThis month day by day, its records and recent years
- California climateThe statewide normals and every place in the state
- Napa State Hospital, CA5 miles from this station, 60.3°F a year
- Vallejo, CA9 miles from this station, 61.6°F a year
- Sonoma, CA11 miles from this station, 59.0°F a year
- Fairfield, CA12 miles from this station, 61.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made