San Isidro weather in December

In December, San Isidro sees average daytime highs of 24°C and overnight lows near 20°C, with 413 mm of rain across 28.8 wet days and about 11.5 hours of daylight. It is the 10th-warmest and 8th-wettest month of the year here.

Day-to-day highs hold fairly steady near 24°C through the month. The sky is clear or mostly clear about 16% of the time in December, and the air most often feels muggy.

Daylight stretches from about 11 h 30 min at the start of December to 11 h 30 min by month's end. Set against the rest of the year, December is San Isidro's 4th-clearest and 11th-windiest month. For the whole year in context, see San Isidro's year-round climate.

Daytime high
24°
10th warmest
Overnight low
20°
2nd coldest
Rainfall
413 mm
28.8 wet days
Daylight
11 h 30 min
5:47 AM – 5:15 PM
Cloud cover
66%
4th clearest
Wind
4 km/h
11th windiest
Solar energy
4.66 kWh/m²
Travel score
4.1
out of 10

San Isidro is district in Pérez Zeledón canton, San José province, Costa Rica.

Density
182/km²
people per km²
Founded
1892

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 24°C through the month.

A typical December day in San Isidro reaches about 24°C in the afternoon and slips back to 20°C overnight — a 4°C spread between the day's warmth and the night's chill. On most days the high lands between 23°C and 25°C. Set against its neighbours, December runs on par with November and on par with January.

15°18°20°23°25°151015202531
Avg high (°C)Avg low (°C)
12420
22420
32420
42420
52420
62420
72420
82420
92420
102420
112420
122420
132420
142420
152420
162420
172420
182420
192420
202420
212420
222420
232420
242420
252420
262420
272420
282420
292420
302420
312420

San Isidro weather by month

How December compares with the rest of the year at a glance. December is the 10th-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan24° / 20°21025.211.54.8
Feb24° / 20°14021.611.75.1
Mar25° / 21°13825.611.94.7
Apr25° / 21°33028.612.23.8
May24° / 21°73030.812.43.4
Jun24° / 21°70929.912.53.4
Jul24° / 21°8333112.53.4
Aug24° / 21°9333112.33.4
Sep24° / 21°8083012.13.4
Oct24° / 20°95230.811.83.4
Nov24° / 20°92429.911.63.5
Dec24° / 20°41328.811.54.1

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 16% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 23% of December, with mostly cloudy or overcast conditions the remaining 61%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
12179
22278
32476
42476
52476
62674
72674
82773
92773
102872
112971
123169
133367
143466
153664
163862
174060
184159
194456
204654
214852
225050
235149
245347
255446
265545
275644
285644
295644
305644
315644

Chance of precipitation in December

Any precipitation

San Isidro gets around 413 mm of rain over 28.8 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 93% and peaks near 98% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%80%100%151015202531
Rain chance (%)
198
298
398
497
597
697
797
897
996
1096
1196
1295
1395
1495
1594
1693
1793
1892
1992
2091
2191
2290
2389
2489
2588
2688
2787
2887
2987
3086
3186

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, December lands in the muggy band about 94% of days. Sticky, muggy-or-worse air turns up on roughly 95% of them.

0%25%50%75%100%151015202531
Humid (%)Muggy (%)Oppressive (%)
13961
23961
33961
43961
53961
63961
73961
83961
93961
103961
113970
123970
134960
144960
154960
165950
175950
186940
196940
207930
217930
227930
238920
248920
258920
268920
278920
289910
299910
309910
319910

Wind in December

Winds average 4 km/h in December.

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

0246810151015202531
Wind speed (km/h)Feels
15calm
25calm
35calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm
314calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 11 h 30 min at the start of December to 11 h 30 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 0 minutes over December. Sunrise moves from 5:40 AM to 5:54 AM, and sunset from 5:09 PM to 5:22 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
111.55:405:09
211.55:405:10
311.55:415:10
411.55:415:10
511.55:425:10
611.55:425:11
711.55:435:11
811.55:435:11
911.55:445:12
1011.55:445:12
1111.55:455:13
1211.55:455:13
1311.55:465:13
1411.55:465:14
1511.55:475:14
1611.55:475:15
1711.55:485:15
1811.55:485:16
1911.55:495:16
2011.55:495:16
2111.55:505:17
2211.55:505:17
2311.55:515:18
2411.55:515:18
2511.55:525:19
2611.55:525:19
2711.55:525:20
2811.55:535:20
2911.55:535:21
3011.55:545:21
3111.55:545:22

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 4.66 kWh/m².

For context, solar energy here swings from a low near 3.71 kWh/m² to a high of 6.24 kWh/m² in March across the year — December's 4.66 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
14.2Bright
24.3Bright
34.3Bright
44.3Bright
54.3Bright
64.4Bright
74.4Bright
84.4Bright
94.4Bright
104.5Bright
114.5Bright
124.5Bright
134.5Bright
144.6Bright
154.6Bright
164.6Bright
174.7Bright
184.7Bright
194.7Bright
204.8Bright
214.8Bright
224.8Bright
234.8Bright
244.9Bright
254.9Bright
264.9Bright
274.9Bright
285.0Bright
295.0Bright
305.0Bright
315.0Bright
Planning a trip in December

Hazard calendar for San Isidro

In seasonPeak

None of San Isidro'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 Isidro's rainy season runs May–November, 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 San Isidro?

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

4.1
Sightseeing
4th-best month of the year
3.4
Beach & pool
5th-best month of the year

December is a reasonable time to visit San Isidro for sightseeing.

What to pack for San Isidro in December

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

In December, San Isidro sees daytime highs around 24°C and nights near 20°C. Pack rain gear. Worth having: light clothes and sun protection. About 29 days see rain.

rain gearlight clothessun protection

Sea temperature near San Isidro in December

The nearest coast averages about 28°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 28 km away) is warmest in March at about 30°C and coldest in November near 28°C.

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

26°28°30°32°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan29Tropical
Feb30Tropical
Mar30Tropical
Apr30Tropical
May29Tropical
Jun29Tropical
Jul29Tropical
Aug29Tropical
Sep29Tropical
Oct28Tropical
Nov28Warm
Dec28Tropical

UV index in San Isidro in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in San Isidro peaks around March 16 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 16 at about 10 (extreme).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeMar 16UV 14Dec 16UV 10
UV index (midday)Level
Jan12Extreme
Feb14Extreme
Mar15Extreme
Apr14Extreme
May13Extreme
Jun13Extreme
Jul12Extreme
Aug13Extreme
Sep13Extreme
Oct12Extreme
Nov12Extreme
Dec10Extreme
Location & terrain

Where is San Isidro?

San Isidro sits at 9.4°N, 83.7°W, 713 m above sea level, in Costa Rica. The nearest listed city is Manuel Antonio, 51 km away.

Manuel AntonioParaísoTurrialbaCartagoSan DiegoPatarráSan MiguelAserrí

Topography around San Isidro

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

Within 3 km, the terrain around San Isidro has only modest variations in elevation — a maximum elevation change of 211 m around an average of 723 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 2,363 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,764 m.

The land around San Isidro is covered by trees (40%), grassland (31%) and artificial surfaces (28%) within 3 km, trees (71%) and grassland (27%) within 16 km, and trees (67%) and water (22%) within 80 km.

3 km
211 m
16 km
2,363 m
80 km
3,764 m
treesgrasslandartificial surfaceswatermangroves
December weather nearby: Manuel Antonio 51 km · Paraíso 56 km · Turrialba 60 km · Cartago 60 km · San Diego 68 km · Patarrá 68 km · San Miguel 69 km · Aserrí 70 km

Costa Rica travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 59% of US
price level, 2025
GDP per capita
$19,970
2025
Happiness
7.4 / 10
World Happiness, 2025
Safe drinking water
81%
of population, 2024
Homicide rate
17.7
per 100k, 2023
Road deaths
14.8
per 100k/yr, 2019
Income group
High
World Bank
English
Moderate
EF EPI 516
Religion
Roman Catholic 48%none 27%Evangelical and Pentecostal 20%other 3%

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 Isidro (9.3674°, -83.6971°, elevation 713 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. 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. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).