San Juan weather in December

In December, San Juan sees average daytime highs of 27°C and overnight lows near 23°C, with 48 mm of rain across 12.2 wet days and about 10.9 hours of daylight. It is the 10th-warmest and 9th-wettest month of the year here.

Day-to-day highs hold fairly steady near 27°C through the month. The sky is clear or mostly clear about 57% of the time in December, and the air most often feels oppressive.

Daylight stretches from about 11 hours at the start of December to 10 h 54 min by month's end. Set against the rest of the year, December is San Juan's 3rd-clearest and 6th-windiest month. For the whole year in context, see San Juan's year-round climate.

Daytime high
27°
10th warmest
Overnight low
23°
5th coldest
Rainfall
48 mm
12.2 wet days
Daylight
10 h 54 min
6:54 AM – 5:47 PM
Cloud cover
42%
3rd clearest
Wind
15 km/h
6th windiest
Solar energy
4.34 kWh/m²
Travel score
6.4
out of 10

San Juan is capital of Puerto Rico.

Density
3,479/km²
people per km²
Founded
1521

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 27°C through the month.

A typical December day in San Juan reaches about 27°C in the afternoon and slips back to 23°C overnight — a 4°C spread between the day's warmth and the night's chill. On most days the high lands between 26°C and 29°C. Set against its neighbours, December runs about 1°C cooler than November and on par with January.

20°23°25°28°30°151015202531
Avg high (°C)Avg low (°C)
12824
22824
32824
42824
52823
62823
72823
82823
92823
102723
112723
122723
132723
142723
152723
162723
172723
182723
192723
202723
212723
222723
232723
242723
252723
262723
272723
282723
292723
302723
312723

How December really feels in San Juan

Once humidity and wind are folded in, December averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

December sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

San Juan weather by month

How December compares with the rest of the year at a glance. December is the 10th-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan27° / 23°3910.4116.8
Feb27° / 22°287.611.47.1
Mar28° / 23°398.411.96.9
Apr28° / 23°721112.45.8
May29° / 24°11216.212.94.7
Jun30° / 25°6813.913.14.5
Jul30° / 25°8016.5134.4
Aug30° / 25°9518.712.64.0
Sep30° / 25°13120.812.13.7
Oct29° / 25°12520.511.64.0
Nov28° / 24°11218.211.14.9
Dec27° / 23°4812.210.96.4

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 57% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 24% of December, with mostly cloudy or overcast conditions the remaining 19%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
17822
27822
37822
47822
58020
68020
78020
88119
98119
108119
118119
128119
138119
148119
158119
168119
178119
188119
198119
208119
218119
228119
238218
248218
258218
268317
278317
288317
298317
308416
318416

Chance of precipitation in December

Any precipitation

San Juan gets around 48 mm of rain over 12.2 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 39% and peaks near 47% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%151015202531
Rain chance (%)
147
246
345
445
544
643
743
842
942
1041
1140
1240
1339
1439
1538
1638
1738
1837
1937
2037
2137
2237
2336
2436
2536
2636
2735
2835
2935
3035
3135

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, December lands in the oppressive band about 67% of days. Sticky, muggy-or-worse air turns up on roughly 97% of them.

0%25%50%75%100%151015202531
Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1220762
2221752
3221752
4222751
5222751
6222751
7223741
8323731
9323731
10324721
11324730
12325720
13326710
14326710
15327700
16328690
17328690
18329680
19330670
20331660
21332650
22333640
23334630
24335620
25336610
26337600
27338590
28339580
29340570
30341560
31343540

Wind in December

Winds average 15 km/h in December.

Across December, daily wind ranges from about 14 km/h on the calmest days to 15 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202531
Wind speed (km/h)Feels
114light breeze
214light breeze
314light breeze
414light breeze
514light breeze
614light breeze
714light breeze
814light breeze
914light breeze
1014light breeze
1114light breeze
1214light breeze
1314light breeze
1415light breeze
1515light breeze
1615light breeze
1715light breeze
1815light breeze
1915light breeze
2015light breeze
2115light breeze
2215light breeze
2315light breeze
2415light breeze
2515light breeze
2615light breeze
2715light breeze
2815light breeze
2915light breeze
3015light breeze
3115light breeze

Sunrise & sunset in December

DaylightNight

Daylight runs from about 11 hours at the start of December to 10 h 54 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 6:45 AM to 7:00 AM, and sunset from 5:43 PM to 5:55 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
111.06:455:43
211.06:465:43
311.06:465:44
410.96:475:44
510.96:475:44
610.96:485:44
710.96:495:45
810.96:495:45
910.96:505:45
1010.96:505:45
1110.96:515:46
1210.96:525:46
1310.96:525:46
1410.96:535:47
1510.96:535:47
1610.96:545:47
1710.96:545:48
1810.96:555:48
1910.96:555:49
2010.96:565:49
2110.96:565:50
2210.96:575:50
2310.96:575:51
2410.96:585:51
2510.96:585:52
2610.96:585:52
2710.96:595:53
2810.96:595:53
2910.97:005:54
3010.97:005:54
3110.97:005:55

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 4.34 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 4.34 kWh/m² to a high of 6.56 kWh/m² in June across the year — December's 4.34 kWh/m² sits near the bottom.

012345151015202531
Solar energy (kWh/m²)Level
14.4Bright
24.4Bright
34.4Bright
44.4Bright
54.4Bright
64.4Bright
74.4Bright
84.4Bright
94.4Bright
104.4Bright
114.4Bright
124.4Bright
134.3Bright
144.3Bright
154.3Bright
164.3Bright
174.3Bright
184.3Bright
194.3Bright
204.3Bright
214.3Bright
224.3Bright
234.3Bright
244.3Bright
254.3Bright
264.3Bright
274.3Bright
284.3Bright
294.3Bright
304.4Bright
314.4Bright
Planning a trip in December

Hazard calendar for San Juan

In seasonPeak

None of San Juan's seasonal hazards are active in December. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

San Juan sits in the Atlantic hurricane belt; the season peaks August–October.

San Juan sees seasonal dust haze (July), heaviest in July.

Atlantic hurricane
Dust
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is December a good time to visit San Juan?

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

6.4
Sightseeing
4th-best month of the year
6.7
Beach & pool
5th-best month of the year

December is a reasonable time to visit San Juan for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for San Juan in December

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

In December, San Juan sees daytime highs around 27°C and nights near 23°C. Pack light clothes. Worth having: rain gear. About 12 days see rain.

light clothesrain gear

Sea temperature near San Juan in December

The nearest coast averages about 27°C 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 18 km away) is warmest in September at about 29°C and coldest in February near 26°C.

The water stays above 20°C all year — warm enough for a swim any month.

24°26°28°30°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan27Warm
Feb26Warm
Mar26Warm
Apr27Warm
May27Warm
Jun28Warm
Jul28Tropical
Aug29Tropical
Sep29Tropical
Oct29Tropical
Nov28Tropical
Dec27Warm

UV index in San Juan in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in San Juan peaks around April 13 at about 13 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 16 at about 7 (high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecVery highExtremeVery highApr 13UV 13Dec 16UV 7
UV index (midday)Level
Jan8Very high
Feb10Extreme
Mar12Extreme
Apr13Extreme
May11Extreme
Jun12Extreme
Jul12Extreme
Aug12Extreme
Sep12Extreme
Oct10Very high
Nov8Very high
Dec7High

Air quality in San Juan 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 San Juan is worst in July — around 24 µg/m³ PM2.5 (moderate), about 4.6× the cleanest month (January, 5 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1324 µg/m³Jan 15 µg/m³
PM2.5 (µg/m³)Level
Jan5Good
Feb7Good
Mar7Good
Apr8Good
May14Moderate
Jun23Moderate
Jul24Moderate
Aug20Moderate
Sep15Moderate
Oct15Moderate
Nov8Good
Dec5Good
Location & terrain

Where is San Juan?

San Juan sits at 18.5°N, 66.1°W, 7 m above sea level, in Puerto Rico. The nearest listed city is Cataño, 3.0 km away.

Trujillo AltoCarolinaCaguas

Topography around San Juan

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of San Juan.

Within 3 km, the terrain around San Juan has only modest variations in elevation — a maximum elevation change of 42 m around an average of 2 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 289 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,308 m.

The land around San Juan is covered by water (81%) within 3 km, water (56%) and artificial surfaces (24%) within 16 km, and water (58%) and trees (32%) within 80 km.

3 km
42 m
16 km
289 m
80 km
1,308 m
treesgrasslandartificial surfacesbare terrainwaterwetlandmangroves
December weather nearby: Cataño 3.0 km · Levittown 8.0 km · Bayamón 9.0 km · Guaynabo 12 km · Candelaria 13 km · Trujillo Alto 16 km · Carolina 18 km · Caguas 27 km

Puerto Rico travel facts

Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 78% of US
price level, 2025
GDP per capita
$40,620
2025
Happiness
7.0 / 10
World Happiness, 2015
Safe drinking water
99%
of population, 2024
Homicide rate
14.6
per 100k, 2023
Income group
High
World Bank
Religion
Roman Catholic 56%Protestant 33%none 7%other 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 San Juan (18.4663°, -66.1057°, elevation 7 m), 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). 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).