Fullerton weather in January

In January, Fullerton sees average daytime highs of 64°F and overnight lows near 49°F, with 2.8 in of rain across 5.2 wet days and about 10 hours of daylight. It is the 12th-warmest and 2nd-wettest month of the year here.

Day-to-day highs hold fairly steady near 64°F through the month. The sky is clear or mostly clear about 47% of the time in January, and the air most often feels dry.

Daylight stretches from about 9 h 48 min at the start of January to 10 h 18 min by month's end. Set against the rest of the year, January is Fullerton's 11th-clearest and 10th-windiest month. For the whole year in context, see Fullerton's year-round climate.

Daytime high
64°
12th warmest
Overnight low
49°
2nd coldest
Rainfall
2.8 in
5.2 wet days
Daylight
10 hours
7:02 AM – 5:00 PM
Cloud cover
47%
11th clearest
Wind
4 mph
10th windiest
Solar energy
3.13 kWh/m²
Travel score
6.8
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 January

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 64°F through the month.

A typical January day in Fullerton reaches about 64°F in the afternoon and slips back to 49°F overnight — a 15°F spread between the day's warmth and the night's chill. On most days the high lands between 58°F and 73°F. Set against its neighbours, January runs on par with December and on par with February.

40°50°60°70°80°151015202531
Avg high (°F)Avg low (°F)
16448
26448
36448
46448
56448
66449
76449
86449
96449
106449
116449
126449
136549
146549
156549
166549
176549
186549
196549
206549
216549
226549
236549
246549
256549
266549
276549
286549
296549
306549
316549

Fullerton weather by month

How January compares with the rest of the year at a glance. January is the 12th-warmest and 2nd-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 January

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 47% of the time in January.

Beyond those clear spells, partly cloudy skies cover about 13% of January, with mostly cloudy or overcast conditions the remaining 40%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15941
25941
35842
45842
55842
65842
75842
85842
95941
105941
115941
125941
136040
146040
156040
166040
176040
186040
196040
206040
216139
226040
236040
246040
256139
266139
276139
286139
296238
306238
316238

Chance of precipitation in January

Any precipitation

Fullerton gets around 2.8 in of rain over 5.2 wet days in January. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 17% and peaks near 18% on the wettest days.

0%10%20%30%151015202531
Rain chance (%)
118
218
318
418
518
618
718
818
918
1018
1118
1217
1317
1417
1517
1617
1717
1817
1917
2016
2116
2216
2316
2416
2516
2616
2716
2816
2916
3016
3116

Humidity in January

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, January lands in the dry band about 94% 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
5955
6955
7946
8946
9946
10937
11937
12928
13928
14928
15928
16928
17928
18928
19928
20937
21937
22937
23946
24946
25955
26955
27955
28964
29964
30964
31964

Wind in January

Winds average 4 mph in January.

Across January, 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
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm
315calm

Sunrise & sunset in January

DaylightNight

Daylight runs from about 9 h 48 min at the start of January to 10 h 18 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 30 minutes over January. Sunrise moves from 7:01 AM to 6:56 AM, and sunset from 4:48 PM to 5:14 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.87:014:48
29.87:024:49
39.87:024:50
49.87:024:50
59.87:024:51
69.87:024:52
79.87:024:53
89.97:024:54
99.97:024:54
109.97:024:55
119.97:024:56
129.97:024:57
139.97:024:58
149.97:024:59
1510.07:024:59
1610.07:025:00
1710.07:015:01
1810.07:015:02
1910.07:015:03
2010.17:015:04
2110.17:005:05
2210.17:005:06
2310.17:005:07
2410.16:595:08
2510.26:595:09
2610.26:585:10
2710.26:585:11
2810.26:575:11
2910.36:575:12
3010.36:565:13
3110.36:565:14

Solar energy in January

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in January, about 3.13 kWh/m².

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 — January's 3.13 kWh/m² sits near the bottom.

01234151015202531
Solar energy (kWh/m²)Level
13.0Moderate
23.0Moderate
33.0Moderate
43.0Moderate
53.0Moderate
63.0Moderate
73.0Moderate
83.0Moderate
93.0Moderate
103.0Moderate
113.0Moderate
123.1Moderate
133.1Moderate
143.1Moderate
153.1Moderate
163.1Moderate
173.2Moderate
183.2Moderate
193.2Moderate
203.3Moderate
213.3Moderate
223.3Moderate
233.3Moderate
243.4Moderate
253.4Moderate
263.4Moderate
273.5Moderate
283.5Moderate
293.5Moderate
303.5Moderate
313.6Moderate
Planning a trip in January

Is January a good time to visit Fullerton?

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

6.8
Sightseeing
11th-best month of the year
2.3
Beach & pool
12th-best month of the year

January is a reasonable time to visit Fullerton for sightseeing.

What to pack for Fullerton in January

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

In January, Fullerton sees daytime highs around 64°F and nights near 49°F. Little to plan around — just the basics. About 5 days see rain.

Sea temperature near Fullerton in January

The nearest coast averages about 59°F in January — 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 January

LowModerateHighVery highExtreme

Clear-sky midday UV in January peaks around 4 — enough to warrant sun protection. 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 January

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where January 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
January 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).