Napa weather in December

In December, Napa sees average daytime highs of 57°F and overnight lows near 42°F, with 4.3 in of rain across 9.3 wet days and about 9.4 hours of daylight. It is the 12th-warmest and 3rd-wettest month of the year here.

Highs ease over the month, from about 59°F in the first days to 56°F by the end. The sky is clear or mostly clear about 35% of the time in December, and the air most often feels dry.

Daylight stretches from about 9 h 30 min at the start of December to 9 h 24 min by month's end. Set against the rest of the year, December is Napa's 10th-clearest and 9th-windiest month. For the whole year in context, see Napa's year-round climate.

Daytime high
57°
12th warmest
Overnight low
42°
2nd coldest
Rainfall
4.3 in
9.3 wet days
Daylight
9 h 18 min
7:25 AM – 4:46 PM
Cloud cover
58%
10th clearest
Wind
5 mph
9th windiest
Solar energy
2.08 kWh/m²
Travel score
4.3
out of 10

Napa is city in Napa County, California, United States.

Density
1,721/km²
people per km²
Founded
1872

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 59°F in the first days to 56°F by the end.

A typical December day in Napa reaches about 57°F in the afternoon and slips back to 42°F overnight — a 16°F spread between the day's warmth and the night's chill. On most days the high lands between 52°F and 63°F. Set against its neighbours, December runs about 7°F cooler than November and on par with January.

30°40°50°60°70°151015202531
Avg high (°F)Avg low (°F)
16043
26043
35943
45943
55943
65943
75843
85843
95842
105842
115842
125842
135742
145742
155742
165742
175742
185741
195741
205741
215641
225641
235641
245641
255641
265641
275641
285641
295641
305641
315641

Napa weather by month

How December compares with the rest of the year at a glance. December is the 12th-warmest and 3rd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan58° / 42°4.69.49.64.3
Feb61° / 44°4.68.610.55.1
Mar65° / 46°3.48.411.76.2
Apr69° / 48°1.54.9137.4
May76° / 52°0.83.2148.4
Jun82° / 56°0.20.914.68.1
Jul84° / 57°0.00.114.47.6
Aug84° / 57°0.00.213.57.5
Sep83° / 56°0.10.412.38.0
Oct76° / 52°1.02.9118.5
Nov65° / 46°2.25.99.96.5
Dec57° / 42°4.39.39.44.3

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 35% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 12% of December, with mostly cloudy or overcast conditions the remaining 53%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15149
25050
34951
44852
54852
64753
74753
84555
94555
104555
114555
124555
134654
144654
154555
164654
174753
184852
194852
204753
214852
224852
234852
244753
254852
264753
274654
284654
294555
304456
314456

Chance of precipitation in December

Any precipitation

Napa gets around 4.3 in of rain over 9.3 wet days in December. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 30% and peaks near 32% on the wettest days.

0%10%20%30%40%151015202531
Rain chance (%)
128
229
329
430
531
631
731
832
932
1032
1132
1232
1331
1431
1531
1630
1730
1830
1930
2029
2129
2229
2329
2429
2529
2629
2728
2828
2928
3028
3129

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

Most of December feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, December lands in the dry band about 97% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)
1973
2964
3964
4964
5964
6964
7964
8964
9964
10964
11964
12964
13964
14964
15973
16973
17973
18973
19982
20982
21982
22982
23982
24982
25982
26982
27982
28982
29982
30982
31982

Wind in December

Winds average 5 mph in December.

Across December, daily wind ranges from about 4 mph on the calmest days to 5 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
304calm
314calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 9 h 30 min at the start of December to 9 h 24 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 6 minutes over December. Sunrise moves from 7:13 AM to 7:31 AM, and sunset from 4:45 PM to 4:53 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.57:134:45
29.57:144:45
39.57:154:44
49.57:164:44
59.57:174:44
69.47:174:44
79.47:184:44
89.47:194:44
99.47:204:44
109.47:214:44
119.47:214:45
129.47:224:45
139.47:234:45
149.47:244:45
159.47:244:45
169.37:254:46
179.37:264:46
189.37:264:46
199.37:274:47
209.37:274:47
219.37:284:48
229.37:284:48
239.37:294:49
249.37:294:49
259.37:294:50
269.37:304:50
279.37:304:51
289.37:314:51
299.47:314:52
309.47:314:53
319.47:314:53

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 2.08 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 2.08 kWh/m² to a high of 8.05 kWh/m² in July across the year — December's 2.08 kWh/m² sits near the bottom.

0123151015202531
Solar energy (kWh/m²)Level
12.2Moderate
22.2Moderate
32.2Moderate
42.1Moderate
52.1Moderate
62.1Moderate
72.1Moderate
82.1Moderate
92.0Moderate
102.0Moderate
112.0Moderate
122.0Moderate
132.0Moderate
142.0Moderate
152.0Moderate
162.0Moderate
172.0Moderate
182.0Moderate
192.0Moderate
202.0Moderate
212.0Moderate
222.1Moderate
232.1Moderate
242.1Moderate
252.1Moderate
262.1Moderate
272.1Moderate
282.1Moderate
292.1Moderate
302.1Moderate
312.1Moderate
Planning a trip in December

Hazard calendar for Napa

In seasonPeak

In December, Napa sits inside its rainy season season. The full year is below, with each hazard's peak months called out.

Napa's rainy season runs November–March, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is December a good time to visit Napa?

Our two travel scores rate December for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

4.3
Sightseeing
11th-best month of the year
0.1
Beach & pool
11th-best month of the year

December is a reasonable time to visit Napa for sightseeing.

What to pack for Napa in December

From December's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In December, Napa sees daytime highs around 57°F and nights near 42°F. Worth packing: a warm layer and rain gear. About 9 days see rain.

a warm layerrain gear

Sea temperature near Napa in December

The nearest coast averages about 54°F in December — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 35 mi away) is warmest in September at about 58°F and coldest in April near 53°F.

The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.

52°54°56°58°60°JanFebMarAprMayJunJulAugSepOctNovDecbracingcool
Sea temperature (°F)Comfort
Jan53Bracing
Feb53Bracing
Mar54Bracing
Apr53Bracing
May53Bracing
Jun54Bracing
Jul56Bracing
Aug58Bracing
Sep58Bracing
Oct57Bracing
Nov55Bracing
Dec54Bracing

UV index in Napa in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 2. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Napa peaks around June 23 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 13 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highHighModerateJun 23UV 10Dec 13UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar5Moderate
Apr6High
May9Very high
Jun10Extreme
Jul10Extreme
Aug9Very high
Sep6High
Oct5High
Nov2Moderate
Dec2Low

Air quality in Napa in December

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where December falls, not just the annual average.

Air quality in Napa is worst in September — around 29 µg/m³ PM2.5 (moderate), about 4.2× the cleanest month (June, 7 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

010203040JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateSep 1829 µg/m³Jun 127 µg/m³
PM2.5 (µg/m³)Level
Jan13Moderate
Feb13Moderate
Mar13Moderate
Apr10Good
May8Good
Jun7Good
Jul10Good
Aug25Moderate
Sep29Moderate
Oct27Moderate
Nov16Moderate
Dec12Good
Location & terrain

Where is Napa?

Napa sits at 38.3°N, 122.3°W, 20 ft above sea level, in United States. The nearest listed city is American Canyon, 8.7 mi away.

Topography around Napa

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Napa.

Within 2 miles, the terrain around Napa has only modest variations in elevation — a maximum elevation change of 492 ft around an average of 79 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,585 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,895 ft.

The land around Napa is covered by artificial surfaces (45%) and trees (33%) within 2 miles, trees (38%) and grassland (38%) within 10 miles, and trees (29%) and grassland (29%) within 50 miles.

2 miles
492 ft
10 miles
2,585 ft
50 miles
4,895 ft
treesshrubsgrasslandcroplandartificial surfaceswaterwetland
December weather nearby: American Canyon 8.7 mi · Agua Caliente 11 mi · Vallejo 14 mi · Fairfield 14 mi · Suisun 14 mi · Vacaville 17 mi · Benicia 19 mi · Hercules 19 mi

United States travel facts

Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 100% of US
price level, 2025
GDP per capita
$90,027
2025
Happiness
6.8 / 10
World Happiness, 2025
Safe drinking water
98%
of population, 2024
Homicide rate
5.8
per 100k, 2023
Road deaths
12.7
per 100k/yr, 2019
Income group
High
World Bank
Religion
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Napa (38.2971°, -122.2855°, elevation 20 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).