San Juan
Puerto Rico, USA
Long-term weather forecast
Long-term weather forecast

May weather forecast and climate
San Juan, PR

An old fort building and a view of the stunning San Juan city, Puerto Rico, with a clear view of the calm waterfront
An old fort building and a view of the stunning San Juan city, Puerto Rico, with a clear view of the calm waterfront
The last month of the spring, May, is another tropical month in San Juan, Puerto Rico, with temperature in the range of an average high of 87.4°F (30.8°C) and an average low of 76.3°F (24.6°C).

Temperature

In May, the average high-temperature is practically the same as in April - a still hot 87.4°F (30.8°C). In San Juan, the average low-temperature is 76.3°F (24.6°C).

Heat index

In May, the average heat index is evaluated at a torrid 101.3°F (38.5°C). Take extra precautions, as heat cramps and heat exhaustion are possible. Sustained activity may result in heatstroke.
Note that heat index values are valued for light wind and location in the shade. With the exposure to direct sunlight, the heat index may be increased by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like', 'apparent temperature', 'felt air temperature', or 'real feel', combines air temperature and relative humidity to represent a human perceived temperature equivalent. Additional factors like activity, metabolic differences, differences in body mass, height, and shape, and wind affect individual temperature impact. Bear in mind that direct sunshine exposure increases weather impact, and may raise heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly important for children. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.
Perspiration is the human body's physiological response to high temperatures and is an attempt to lower body temperature through evaporation of sweat. With a lot of moisture in the air, the evaporation process is not as effective, and the body does not cool down as efficiently, creating a perception of overheating. When heat gain exceeds the level the body can remove, body temperature begins to rise, and heat-related illnesses and disorders may develop.

Humidity

In May, the average relative humidity is 74.9%.

Rainfall

In San Juan, during 15.7 rainfall days, 7.2" (182mm) of precipitation is typically accumulated. Throughout the year, in San Juan, there are 198.5 rainfall days, and 70.6" (1794mm) of precipitation is accumulated.

Ocean temperature

In San Juan, in May, the average water temperature is 81.5°F (27.5°C).
Note: For swimming, diving, and other water activities, temperatures between 77°F (25°C) and 84.2°F (29°C) are perceived as very enjoyable and pleasurable for prolonged periods without feeling uncomfortable.

Daylight

In San Juan, Puerto Rico, the average length of the day in May is 13h.

Sunshine

In San Juan, Puerto Rico, the average sunshine is 8.2h.

UV index

March through September, with an average maximum UV index of 12, are months with the highest UV index in San Juan. A UV Index of 11, and more, symbolizes an extreme threat to health from unsafe exposure to the UV radiation for average individuals.
Note: The average daily UV index of 12 in May transform into the following instructions:
Take all required precautions, as unprotected skin and eyes can burn in minutes. The Sun's UV radiation is most powerful between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the direct sun during these hours. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects. A broad-spectrum sunscreen of SPF 30+ should be liberally applied and re-applied every two hours, and immediately after an outdoor workout or a swim. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.

What is the temperature in May in San Juan?

The average high-temperature, in May, in San Juan, Puerto Rico, is 87.4°F (30.8°C), while the average low-temperature is 76.3°F (24.6°C). In May, the average heat index (a.k.a. 'real feel', 'felt air temperature'), that represents influence of the relative humidity to air temperaure, is calculated to 101.3°F (38.5°C).

What is the average humidity in May in San Juan?

The average relative humidity in May in San Juan, Puerto Rico, is 74.9%.

How many days does it rain in May in San Juan?

In San Juan, Puerto Rico, during May, the rain falls for 15.7 days and regularly aggregates up to 7.2" (182mm) of precipitation.

What is the water temperature in May in San Juan?

In San Juan, in May, the average water temperature is 81.5°F (27.5°C). Water temperature between 77°F (25°C) and 84.2°F (29°C) is regarded as very warm and enjoyable by all. With these temperatures, water activities are pleasurable, without feeling uncomfortable for prolonged periods.

How many hours of daylight does San Juan have in May?

In May, the average length of the day is 13h.

How many hours of sunshine does San Juan have in May?

The average sunshine in May in San Juan, Puerto Rico, is 8.2h.

When is the highest UV index in San Juan?

Months with the highest UV index in San Juan, Puerto Rico, are March through September, with an average maximum UV index of 12.

How high is the UV index in May in San Juan?

In San Juan, the average daily maximum UV index in May is 12. A UV Index value of 11, and more, symbolizes an ultimate hazard to health from unprotected exposure to the UV radiation.
Average temperature in May - San Juan, PR
  • Average high temperature in May: 87.5°F

Warmest months (with the highest average high temperature) are August and September (89.2°F).
The month with the lowest average high temperature is January (83.2°F).

  • Average low temperature in May: 76.3°F

The month with the highest average low temperature is August (78.2°F).
Coldest months (with the lowest average low temperature) are January and February (72°F).

Average humidity in May - San Juan, PR
  • Average humidity in May: 74.9%

The month with the highest relative humidity is October (76.9%).
The month with the lowest relative humidity is March (71%).

Average rainfall in May - San Juan, PR
  • Average rainfall in May: 7.2"

The wettest month (with the highest rainfall) is August (7.7").
The driest month (with the lowest rainfall) is March (3.1").

Average rainfall days in May - San Juan, PR
  • Average rainfall days in May: 15.7 days

Months with the highest number of rainy days are November and December (19.6 days).
The month with the lowest number of rainy days is March (12.2 days).

Average sea temperature in May - San Juan, PR
  • Average sea temperature in May: 81.5°F

The best month for swimming (with the highest average sea temperature) is September (84.9°F).
The coldest month (with the lowest average sea temperature) is February (78.9°F).

Average daylight in May / Average sunshine in May - San Juan, PR
  • Average daylight in May: 13h

The month with the longest days is June (Average daylight: 13.2h).
The month with shortest days is December (Average daylight: 11h).

  • Average sunshine in May: 8.2h

Months with most sunshine are March and July (Average sunshine: 9.1h).
The month with least sunshine is November (Average sunshine: 6.7h).

Average UV index in May - San Juan, PR
  • Average UV index in May: 12

Months with the highest UV index are March, April, May, June, July, August and September (UV index 12).
Months with the lowest UV index are January and December (UV index 8).