Fullerton weather in December

In December, Fullerton sees average daytime highs of 65°F and overnight lows near 49°F, with 1.9 in of rain across 4.9 wet days and about 9.8 hours of daylight. It is the 10th-warmest and 3rd-wettest month of the year here.

Day-to-day highs hold fairly steady near 65°F through the month. The sky is clear or mostly clear about 51% of the time in December, and the air most often feels dry.

Daylight stretches from about 9 h 54 min at the start of December to 9 h 48 min by month's end. Set against the rest of the year, December is Fullerton's 9th-clearest and 9th-windiest month. For the whole year in context, see Fullerton's year-round climate.

Daytime high
65°
10th warmest
Overnight low
49°
2nd coldest
Rainfall
1.9 in
4.9 wet days
Daylight
9 h 48 min
6:55 AM – 4:41 PM
Cloud cover
42%
9th clearest
Wind
5 mph
9th windiest
Solar energy
2.98 kWh/m²
Travel score
6.9
out of 10

Fullerton is city in Orange County, California, United States.

Density
2,423/km²
people per km²
Founded
1887

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

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 65°F through the month.

A typical December day in Fullerton reaches about 65°F in the afternoon and slips back to 49°F overnight — a 16°F spread between the day's warmth and the night's chill. On most days the high lands between 58°F and 72°F. Set against its neighbours, December runs about 5°F cooler than November and on par with January.

40°50°60°70°80°151015202531
Avg high (°F)Avg low (°F)
16751
26651
36651
46650
56650
66550
76550
86550
96550
106550
116549
126549
136549
146449
156449
166449
176449
186448
196448
206448
216448
226448
236448
246448
256448
266448
276448
286448
296448
306448
316448

Fullerton weather by month

How December compares with the rest of the year at a glance. December is the 10th-warmest and 3rd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan64° / 49°2.85.2106.8
Feb65° / 50°3.16.110.76.7
Mar66° / 53°1.85.111.77.0
Apr69° / 55°0.72.612.87.9
May71° / 58°0.31.513.78.3
Jun74° / 61°0.10.314.29.1
Jul79° / 64°0.10.4149.0
Aug81° / 65°0.00.113.38.9
Sep80° / 64°0.10.512.28.8
Oct76° / 60°0.61.911.18.8
Nov70° / 54°0.72.410.28.1
Dec65° / 49°1.94.99.86.9

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 51% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 13% of December, with mostly cloudy or overcast conditions the remaining 36%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
16832
26832
36733
46634
56634
66535
76535
86535
96535
106436
116436
126436
136436
146436
156436
166436
176436
186436
196535
206535
216535
226535
236436
246436
256436
266238
276238
286139
296139
306139
316040

Chance of precipitation in December

Any precipitation

Fullerton gets around 1.9 in of rain over 4.9 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 16% and peaks near 18% on the wettest days.

0%10%20%30%151015202531
Rain chance (%)
113
213
313
414
514
614
714
815
915
1015
1116
1216
1316
1417
1517
1617
1717
1817
1917
2017
2117
2217
2317
2417
2517
2617
2717
2817
2917
3018
3118

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 93% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)
188111
288111
388111
489101
589101
689101
789101
890100
990100
109190
119190
129190
139280
149370
159370
169460
179550
189550
199640
209640
219730
229730
239730
249730
259730
269730
279730
289730
299730
309730
319730

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
14calm
24calm
34calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm
315calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 9 h 54 min at the start of December to 9 h 48 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 6:44 AM to 7:02 AM, and sunset from 4:39 PM to 4:48 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.96:444:39
29.96:454:39
39.96:464:39
49.96:474:39
59.96:474:39
69.86:484:39
79.86:494:39
89.86:504:39
99.86:504:39
109.86:514:39
119.86:524:39
129.86:534:40
139.86:534:40
149.86:544:40
159.86:554:40
169.86:554:41
179.86:564:41
189.86:564:41
199.76:574:42
209.76:574:42
219.76:584:43
229.76:584:43
239.76:594:43
249.76:594:44
259.77:004:45
269.87:004:45
279.87:004:46
289.87:014:46
299.87:014:47
309.87:014:47
319.87:024:48

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 2.98 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 2.98 kWh/m² to a high of 7.89 kWh/m² in June across the year — December's 2.98 kWh/m² sits near the bottom.

01234151015202531
Solar energy (kWh/m²)Level
13.1Moderate
23.1Moderate
33.0Moderate
43.0Moderate
53.0Moderate
63.0Moderate
73.0Moderate
83.0Moderate
92.9Moderate
102.9Moderate
112.9Moderate
122.9Moderate
132.9Moderate
142.9Moderate
152.9Moderate
162.9Moderate
172.9Moderate
182.9Moderate
192.9Moderate
202.9Moderate
212.9Moderate
222.9Moderate
232.9Moderate
243.0Moderate
253.0Moderate
263.0Moderate
273.0Moderate
283.0Moderate
293.0Moderate
303.0Moderate
313.0Moderate
Planning a trip in December

Is December a good time to visit Fullerton?

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

6.9
Sightseeing
10th-best month of the year
2.4
Beach & pool
10th-best month of the year

December is a reasonable time to visit Fullerton for sightseeing.

What to pack for Fullerton in December

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

In December, Fullerton sees daytime highs around 65°F and nights near 49°F. Little to plan around — just the basics. About 5 days see rain.

Sea temperature near Fullerton in December

The nearest coast averages about 60°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 17 mi away) is warmest in August at about 69°F and coldest in February near 59°F.

It's comfortable for a long swim from Jul 13 to Sep 28 — about 2.6 months when the water holds above 68°F.

60°65°70°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingcomfortable to swim
Sea temperature (°F)Comfort
Jan59Cool
Feb59Cool
Mar59Cool
Apr60Cool
May63Cool
Jun65Cool
Jul68Refreshing
Aug69Refreshing
Sep69Refreshing
Oct67Cool
Nov64Cool
Dec60Cool

UV index in Fullerton in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 3. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Fullerton peaks around July 11 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 16 at about 3 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 11 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateVery highExtremeVery highHighModerateJul 11UV 11Dec 16UV 3
UV index (midday)Level
Jan4Moderate
Feb5Moderate
Mar5Moderate
Apr8Very high
May8Very high
Jun11Extreme
Jul11Extreme
Aug10Extreme
Sep8Very high
Oct6High
Nov3Moderate
Dec3Moderate

Air quality in Fullerton 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 Fullerton is worst in September — around 49 µg/m³ PM2.5 (poor), about 4.0× the cleanest month (May, 12 µg/m³).

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

0204060JanFebMarAprMayJunJulAugSepOctNovDecModeratePoorModerateSep 1447 µg/m³May 1713 µg/m³
PM2.5 (µg/m³)Level
Jan18Moderate
Feb19Moderate
Mar19Moderate
Apr17Moderate
May12Moderate
Jun17Moderate
Jul19Moderate
Aug32Moderate
Sep49Poor
Oct21Moderate
Nov21Moderate
Dec18Moderate
Location & terrain

Where is Fullerton?

Fullerton sits at 33.9°N, 117.9°W, 164 ft above sea level, in United States. The nearest listed city is Anaheim, 2.5 mi away.

Topography around Fullerton

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

Within 2 miles, the terrain around Fullerton has only modest variations in elevation — a maximum elevation change of 384 ft around an average of 197 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,654 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 10,010 ft.

The land around Fullerton is covered by artificial surfaces (83%) within 2 miles, artificial surfaces (76%) within 10 miles, and water (29%) and artificial surfaces (25%) within 50 miles.

2 miles
384 ft
10 miles
1,654 ft
50 miles
10,010 ft
treesshrubsgrasslandcroplandartificial surfacesbare terrainwater
December weather nearby: Anaheim 2.5 mi · Placentia 3.1 mi · Brea 3.7 mi · Buena Park 4.3 mi · La Habra 4.3 mi · La Mirada 6.2 mi · Stanton 6.2 mi · Yorba Linda 6.8 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 Fullerton (33.8703°, -117.9253°, elevation 164 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).