September 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

What is the warmest month in San Juan?

August and September, with an average high-temperature of 89.2°F (31.8°C), are warmest months in San Juan, Puerto Rico.

What is the temperature in September in San Juan?

In San Juan, Puerto Rico, in September, the average high-temperature is 89.2°F (31.8°C), and the average low-temperature is 77.7°F (25.4°C).

What is the average humidity in September in San Juan?

In September, the average relative humidity in San Juan, Puerto Rico, is 76.4%.

How much does it rain in San Juan in September?

In September, the rain falls for 17.4 days. Throughout September, 7.4" (188mm) of precipitation is accumulated.

When is the ocean warmest in San Juan?

With an average ocean temperature of 84.9°F (29.4°C), September is the month with the warmest seawater. 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.

What is the water temperature in September in San Juan?

In September, the average ocean temperature in San Juan, Puerto Rico, is 84.9°F (29.4°C). For any water activity, surface water temperatures between 77°F (25°C) and 84.2°F (29°C) are considered as excellent and extremely pleasant for lengthened periods.

What is the month with the highest UV index in San Juan?

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

What is the average UV index in September in San Juan?

In September, the average UV index in San Juan, Puerto Rico, is 12.
Average temperature in September - San Juan, PR
  • Average high temperature in September: 31.8°C

Warmest months (with the highest average high temperature) are August and September (31.8°C).
The month with the lowest average high temperature is January (28.4°C).

  • Average low temperature in September: 25.4°C

The month with the highest average low temperature is August (25.7°C).
Coldest months (with the lowest average low temperature) are January and February (22.2°C).

Average humidity in September - San Juan, PR
  • Average humidity in September: 76.4%

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

Average rainfall in September - San Juan, PR
  • Average rainfall in September: 188mm

The wettest month (with the highest rainfall) is August (195mm).
The driest month (with the lowest rainfall) is March (79mm).

Average rainfall days in September - San Juan, PR
  • Average rainfall days in September: 17.4 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 September - San Juan, PR
  • Average sea temperature in September: 29.4°C

The best month for swimming (with the highest average sea temperature) is September (29.4°C).
Coldest months (with the lowest average sea temperature) are February and March (26.1°C).

Average daylight in September / Average sunshine in September - San Juan, PR
  • Average daylight in September: 12.2h

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 September: 7.8h

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 September - San Juan, PR
  • Average UV index in September: 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).

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