Napa County, CA Climate: Temperature & Rain by Month
Pulled from NOAA NCEI 1991–2020 normals →: climate measurements used in PlainClimate's documented score
30-year climate normals (1991-2020) from Napa County's primary NOAA station, NAPA CO AP.
The climate verdict for Napa County
A compact 19.7°F seasonal swing gives Napa County, California a steadier-than-extreme annual shape. NOAA reports an annual average of 58°F. It scores 85/100 for climate comfort (excellent), putting it in the top third of station-mapped location scores and exceeding 85% of them.
- 58°F
- annual average temperature (NOAA normal)
- 85/100
- comfort score, above 85% of station-mapped location scores
- 20.2"
- yearly precipitation total
- 261 days
- frost-free days per growing season
Napa County: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USW00093227 · Napa County, CA 58°F mean · 20.2" precip
TEMP-MILD · RANK-UPPER · PHOTO-FINISH · PRCP-DRY · SWING-NARROW · COMF-TOP · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-MILD 58°F
- RANK-UPPER #4,665
- PHOTO-FINISH ≈ Graton
- PRCP-DRY 20.2"
- SWING-NARROW 20°F
- COMF-TOP 85/100
- LOAD-HEAT 2,956 HDD
- STN-1 USW00093227
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Graton, CA (+ 0.1 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every CA station list.
- Napa County (this station) 58°F
- Hot Santa Rosa Sono…, CA 58°F
- Near Graton, CA 58°F
- Near Petaluma, CA 58°F
- Cold Big Sur, CA 57°F
Climate Living Index · Napa County
Napa County: 78/100 · grade B
Napa County publishes 4 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 2 missing weights rescale to 100.
PlainClimate-derived for Napa County, not an official NOAA rating. Rankings still use Comfort Score 85/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Normal heat + freeze calendar | 0 calendar days | 100/100 · A |
| Frost-free season | 261 days/year | 92/100 · A |
| Annual temperature balance | 57.7°F · 9.8° from 67.5°F | 69/100 · C |
| Precipitation balance | 20.2 in · 14.8 from 35 in | 48/100 · D |
Napa County · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Napa County is a temperate Köppen climate: Csb
Coldest-month mean 47.5°F and warmest-month mean 67.2°F place this station in temperate, dry-summer, warm summer climates (Csb). Class Csb is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: temperate, specifically temperate, dry-summer, warm summer.
- Köppen code
- Csb
- Group
- Temperate
- Warmest month
- 67.2°F
- Coldest month
- 47.5°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Napa County sits across the climate record
Three NOAA fields for Napa County's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 68th percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- Drier than 72%
- Napa County's annual total ranks in the drier third of 6,352 measured normals.
- Seasonal temperature swing
- Narrower than 97%
- Warmest-to-coldest month gap for Napa County is compact versus 6,861 complete station-years.
How Napa County compares across U.S. station-mapped locations
Napa County's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
85 Top 15% score exceeds 85% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). Below this entry.
- 60–70: 1,236 station-mapped locations (20%). Below this entry.
- 70–80: 650 station-mapped locations (11%). Below this entry.
- 80–90: 921 station-mapped locations (15%). This entry sits in this band.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|
| January | 57°F (14°C) | 38°F (3°C) | 48°F (9°C) | 4.2" | 8.7 | 0.0 |
| February | 61°F (16°C) | 40°F (4°C) | 50°F (10°C) | 4.0" | 5.4 | 0.0 |
| March | 64°F (18°C) | 42°F (5°C) | 53°F (12°C) | 3.0" | 2.2 | 0.0 |
| April | 68°F (20°C) | 44°F (6°C) | 56°F (13°C) | 1.3" | 1.4 | 0.2 |
| May | 73°F (23°C) | 48°F (9°C) | 61°F (16°C) | 0.8" | 0.0 | 1.2 |
| June | 78°F (26°C) | 52°F (11°C) | 65°F (18°C) | 0.2" | 0.0 | 3.1 |
| July | 79°F (26°C) | 55°F (13°C) | 67°F (19°C) | 0.0" | 0.0 | 2.1 |
| August | 80°F (27°C) | 54°F (12°C) | 67°F (20°C) | 0.0" | 0.0 | 2.8 |
| September | 80°F (27°C) | 51°F (11°C) | 66°F (19°C) | 0.1" | 0.0 | 5.0 |
| October | 75°F (24°C) | 46°F (8°C) | 61°F (16°C) | 0.9" | 0.1 | 1.6 |
| November | 65°F (18°C) | 40°F (5°C) | 53°F (12°C) | 2.0" | 4.9 | 0.0 |
| December | 57°F (14°C) | 38°F (3°C) | 48°F (9°C) | 3.8" | 11.2 | 0.0 |
The year, day by day
The calendar barely moves in Napa County: no date carries a normal high of 90°F or a normal low at freezing. The year runs between 37°F near December 16 and 81°F near August 30.
No freezing date
Not one calendar date in the 1991–2020 record carries a normal low at or below 32°F. The coldest normal low of the year is 37°F around December 16.
Where the wet dates fall
The likeliest wet date is February 18, when 35% of years recorded at least a hundredth of an inch. The driest is July 22 at 1%. Summed across the calendar, that is about 62 wet dates a year.
The widest day
October 4 carries the biggest normal gap between afternoon and dawn, 30°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Napa County.
Monthly Precipitation
Average monthly rainfall
9.9 days with precipitation
9.8 days with precipitation
9.6 days with precipitation
5.9 days with precipitation
3.2 days with precipitation
1.0 days with precipitation
0.1 days with precipitation
0.2 days with precipitation
1.0 days with precipitation
3.2 days with precipitation
7.2 days with precipitation
10.3 days with precipitation
Napa County's wet season runs through the cold months
December, January and February carry 59% of the year's precipitation here, while June through August contribute 1%. That is the cool-season-dominant pattern of the West Coast and the higher inland West, where storm tracks swing south in winter and summer turns dry; the thermometer meanwhile shows an unusually narrow 19.7°F seasonal spread.
- Wettest month
- January, 4.2"
- Driest month
- July, 0.0"
- Wettest three months
- January, February, December (59% of the year)
Shares are computed from this station's own 1991-2020 monthly precipitation normals. A cool-season label means the December-February share reaches 35%. Where snow falls, the monthly figures above report liquid-equivalent precipitation, so a wet winter month is not necessarily a rainy one.
How Napa County's precipitation splits across the calendar
About 61 days a year record measurable precipitation here, carrying 20.2" between them, or roughly 0.33 inches on a typical wet day. That sits in the middle band: neither the many-light-days pattern of the Pacific Northwest and the Great Lakes, nor the few-heavy-events pattern of the Gulf and the desert Southwest.
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year and say nothing about the heaviest single storm on record.
Frost Dates & Growing Season
First Fall Freeze
November 21
50% probability date
Last Spring Freeze
March 5
50% probability date
Growing Season
261 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
2,956
Higher = more heating needed
Cooling Degree Days
315
Higher = more cooling needed
Warmest Month
August
Coldest Month
December
Nationwide similar cities
Other rankable U.S. places outside CA closest to Napa County on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (58°F here).
- Follett, TX 58°F · 0.0°F off
- Wichita, KS 58°F · 0.0°F off
- Williamson, WV 58°F · 0.0°F off
- Clayton, GA 58°F · 0.1°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (20.2" here), excluding temperature-peer places.
- Petersburg, ND 20.2" · 0.0" off
- Rolette, ND 20.2" · 0.0" off
- Brewster, KS 20.3" · 0.0" off
- Eureka, SD 20.3" · 0.0" off
Data-derived climate profile
How Napa County's climate pattern fits together
heating led · moderate · low swing
Heating is the larger measured load in Napa County, at 2,956 degree days versus 315 for cooling. Unlike a strongly continental record, however, its 19.7°F month-to-month range is compact; persistent cool-season demand matters more than a dramatic summer-to-winter reversal.
The frost-free window extends for about 261 days. That is a long calendar measure, but it is not a forecast and does not combine heat, rainfall, soil, or local elevation into a planting recommendation.
Temperature varies within a narrow 19.7°F band across the normal year. August and December mark the typical warm and cold ends of the calendar. The annual average is 58°F. Monthly rows still matter, but they refine a steady profile rather than reveal two climatic extremes.
Napa County's 20.2 inches of annual precipitation falls in PlainClimate's middle band, so “wet” or “dry” is not the leading description. Snowfall is not added to the interpretation because its annual value is missing. Temperature balance and the calendar distribution carry more information than the annual moisture label alone.
These labels group NOAA 1991-2020 normals from Napa County's primary station, so the winter figures are a thirty-year average and not a floor: a single hard season can run well below them. Treat each band as a descriptive range for Napa County, not an official NOAA class or a year-ahead forecast.
Questions about Napa County's climate
How much rain does Napa County get? ▼
How much energy does heating and cooling require in Napa County? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Napa County's primary station: NAPA CO AP (USW00093227). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The conservative exact name-and-state crosswalk finds no Census place match, so PlainClimate treats this as a station-mapped location and does not claim it is a municipality. No exact Gazetteer row for Napa County; facility counts that depend on place identity are therefore an upper bound, not a municipal census.
On this page every temperature, precipitation, and derived score for Napa County comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.