Napa, CA climate
Napa has mild winters and warm summers. A typical July afternoon reaches 86°, a January night drops to 38°, and snow is almost unheard of.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Napa feels like
Winter
Spring
Summer
Fall
Napa weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 57° | 38° | 5.2" | 0 | 12 | 0 | 44° – 51° |
| February | 62° | 41° | 5.1" | 0 | 11 | 0 | 47° – 55° |
| March | 66° | 42° | 3.7" | 0 | 10 | 0 | 49° – 60° |
| April | 71° | 45° | 1.7" | 0 | 7 | 0 | 53° – 62° |
| May | 76° | 49° | 0.9" | 0 | 4 | 0 | 57° – 68° |
| June | 83° | 53° | 0.2" | 0 | 1 | 0 | 64° – 70° |
| July | 86° | 55° | 0.0" | 0 | 0 | 0 | 67° – 74° |
| August | 86° | 54° | 0.1" | 0 | 0 | 0 | 67° – 74° |
| September | 85° | 52° | 0.1" | 0 | 1 | 0 | 65° – 72° |
| October | 78° | 48° | 1.3" | 0 | 4 | 0 | 60° – 68° |
| November | 66° | 42° | 2.7" | 0 | 8 | 0 | 48° – 58° |
| December | 57° | 38° | 5.4" | 0 | 12 | 0 | 44° – 52° |
| Year | 73° | 46° | 26.3" | 0.0" | 68 | 0 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Napa
Napa gets 26 inches of rain and melted snow a year. December is the wettest month and July the driest. Rain or snow falls on about 68 days a year.
About 299 frost-free days a year
In half of years the last 32° night comes by February 12 and the first one by December 4. That leaves about 299 frost-free days for gardens, longer than 95% of U.S. towns.
Heating and cooling a home in Napa
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Napa, 79% of that work is heating and 21% is cooling.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
How Napa compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Napa averaged 1.6° warmer than the 1900s. The biggest change is in January (+2.1°). The shift is larger than in 76% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Napa’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. March swings the most: between 1991 and 2020 its average temperature ranged from 49° to 60°. June is the most reliable, staying within 6°.
Common questions about Napa’s climate
What is the coldest month in Napa?
December, with a typical high of 57° and a low of 38°.
What is the hottest month in Napa?
August, with a typical high of 86° and a low of 54°. About 32 days a year reach 90°.
How much snow does Napa get?
Almost none. A normal year brings 0.0 inches.
When is the first frost in Napa?
In half of years the first 32° night comes by December 4, and the last spring frost by February 12.
What is the rainiest month in Napa?
December, with 5.4 inches of rain and melted snow. The year totals 26 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Napa itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Napa State Hospital, CA (2 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.