San Juan weather in May

In May, San Juan sees average daytime highs of 23°C and overnight lows near 16°C, with 357 mm of rain across 27.8 wet days and about 12.4 hours of daylight. It is the 2nd-warmest and 4th-wettest month of the year here.

Day-to-day highs hold fairly steady near 23°C through the month. The sky is clear or mostly clear about 1% of the time in May, and the air most often feels humid.

Daylight stretches from about 12 h 18 min at the start of May to 12 h 30 min by month's end. Set against the rest of the year, May is San Juan's 7th-clearest and 9th-windiest month. For the whole year in context, see San Juan's year-round climate.

Daytime high
23°
2nd warmest
Overnight low
16°
11th coldest
Rainfall
357 mm
27.8 wet days
Daylight
12 h 30 min
5:19 AM – 5:46 PM
Cloud cover
92%
7th clearest
Wind
4 km/h
9th windiest
Solar energy
4.36 kWh/m²
Travel score
3.8
out of 10

San Juan is district in Tibás canton, San José province, Costa Rica.

Density
7,421/km²
people per km²

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

Temperature in May

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 23°C through the month.

A typical May day in San Juan reaches about 23°C in the afternoon and slips back to 16°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 21°C and 24°C. Set against its neighbours, May runs on par with April and on par with June.

10°15°20°25°151015202531
Avg high (°C)Avg low (°C)
12316
22316
32316
42316
52316
62316
72316
82316
92316
102316
112316
122316
132316
142316
152316
162316
172316
182316
192316
202316
212316
222316
232316
242316
252316
262316
272316
282316
292316
302316
312316

San Juan weather by month

How May compares with the rest of the year at a glance. May is the 2nd-warmest and 4th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan21° / 14°10413.311.56.0
Feb22° / 14°6811.911.76.2
Mar23° / 14°6513.911.96.1
Apr23° / 15°1021812.25.3
May23° / 16°35727.812.43.8
Jun23° / 16°38528.812.63.5
Jul23° / 16°29328.212.53.7
Aug23° / 16°34528.512.33.7
Sep23° / 16°39129.112.13.5
Oct22° / 16°43030.111.83.4
Nov22° / 15°31225.511.54.0
Dec21° / 15°17017.811.45.3

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 1% of the time in May.

Beyond those clear spells, partly cloudy skies cover about 3% of May, with mostly cloudy or overcast conditions the remaining 96%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
1892
2793
3793
4694
5694
6694
7595
8595
9595
10595
11595
12595
13496
14496
15397
16397
17397
18298
19298
20298
21298
22298
23298
24397
25298
26298
27298
28298
29298
30298
31298

Chance of precipitation in May

Any precipitation

San Juan gets around 357 mm of rain over 27.8 wet days in May. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 90% and peaks near 97% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%80%100%151015202531
Rain chance (%)
178
279
380
481
582
682
783
884
985
1086
1186
1287
1388
1489
1590
1691
1792
1892
1993
2094
2194
2295
2395
2496
2596
2697
2797
2897
2997
3097
3197

Humidity in May

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, May lands in the humid band about 81% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)
1233632
2231652
3129682
4128683
5126703
6125713
7123733
8122743
9120754
10119764
11117784
12116785
13114805
14113806
15112816
16011836
1709856
1808857
1908857
2007867
2106886
2206886
2305896
2405896
2505896
2604906
2704906
2804906
2903925
3003925
3103925

Wind in May

Winds average 4 km/h in May.

Across May, 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
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm
314calm

Sunrise & sunset in May

DaylightNight

Daylight runs from about 12 h 18 min at the start of May to 12 h 30 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 12 minutes over May. Sunrise moves from 5:23 AM to 5:18 AM, and sunset from 5:44 PM to 5:50 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
112.35:235:44
212.45:235:44
312.45:225:44
412.45:225:44
512.45:225:44
612.45:215:45
712.45:215:45
812.45:215:45
912.45:215:45
1012.45:205:45
1112.45:205:45
1212.45:205:45
1312.45:205:46
1412.45:195:46
1512.45:195:46
1612.55:195:46
1712.55:195:46
1812.55:195:47
1912.55:185:47
2012.55:185:47
2112.55:185:47
2212.55:185:48
2312.55:185:48
2412.55:185:48
2512.55:185:48
2612.55:185:48
2712.55:185:49
2812.55:185:49
2912.55:185:49
3012.55:185:49
3112.55:185:50

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 4.36 kWh/m².

For context, solar energy here swings from a low near 3.58 kWh/m² to a high of 5.78 kWh/m² in March across the year — May's 4.36 kWh/m² falls in the middle.

024151015202531
Solar energy (kWh/m²)Level
14.9Bright
24.9Bright
34.8Bright
44.8Bright
54.8Bright
64.7Bright
74.7Bright
84.6Bright
94.6Bright
104.5Bright
114.5Bright
124.4Bright
134.4Bright
144.4Bright
154.3Bright
164.3Bright
174.3Bright
184.2Bright
194.2Bright
204.2Bright
214.2Bright
224.2Bright
234.2Bright
244.2Bright
254.2Bright
264.2Bright
274.2Bright
284.2Bright
294.2Bright
304.2Bright
314.2Bright
Planning a trip in May

Is May a good time to visit San Juan?

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

3.8
Sightseeing
7th-best month of the year
3.0
Beach & pool
6th-best month of the year

May is a weaker month for outdoor sightseeing in San Juan.

What to pack for San Juan in May

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

In May, San Juan sees daytime highs around 23°C and nights near 16°C. Pack rain gear. Worth having: light clothes. About 28 days see rain.

rain gearlight clothes

Sea temperature near San Juan in May

The nearest coast averages about 29°C in May — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 61 km away) is warmest in April at about 29°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°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan29Tropical
Feb29Tropical
Mar29Tropical
Apr29Tropical
May29Tropical
Jun29Tropical
Jul29Tropical
Aug29Tropical
Sep29Tropical
Oct28Tropical
Nov28Warm
Dec28Tropical

UV index in San Juan in May

LowModerateHighVery highExtreme

Clear-sky midday UV in May peaks around 13 (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 Juan peaks around March 19 at about 15 (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 19UV 15Dec 16UV 10
UV index (midday)Level
Jan12Extreme
Feb14Extreme
Mar15Extreme
Apr14Extreme
May13Extreme
Jun13Extreme
Jul13Extreme
Aug13Extreme
Sep13Extreme
Oct12Extreme
Nov12Extreme
Dec10Extreme

Air quality in San Juan in May

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in San Juan is worst in May — around 19 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (January, 9 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodMay 1718 µg/m³Jan 149 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb10Good
Mar11Good
Apr17Moderate
May19Moderate
Jun17Moderate
Jul18Moderate
Aug17Moderate
Sep16Moderate
Oct14Moderate
Nov12Good
Dec10Good
Location & terrain

Where is San Juan?

San Juan sits at 10.0°N, 84.1°W, 1,114 m above sea level, in Costa Rica. The nearest listed city is Colima, 1.0 km away.

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 220 m around an average of 1,157 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,764 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,674 m.

The land around San Juan is covered by artificial surfaces (65%) and trees (27%) within 3 km, trees (58%) and artificial surfaces (27%) within 16 km, and trees (71%) within 80 km.

3 km
220 m
16 km
1,764 m
80 km
3,674 m
treesgrasslandcroplandartificial surfaceswater
May weather nearby: Colima 1.0 km · Calle Blancos 2.0 km · Guadalupe 3.0 km · San Jose 3.0 km · San Vicente 3.0 km · San Vicente de Moravia 3.0 km · San Pablo 4.0 km · San Pedro 5.0 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 Juan (9.9619°, -84.0788°, elevation 1,114 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. 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).