San Juan Rainfall & Precipitation: Monthly Averages and Year-Round Insights

This page shows the average amount of rainfall per month in San Juan. The numbers are calculated over a 30-year period to provide a reliable average. Let’s explore the details in depth to provide you with a complete overview.

San Juan has a notably wet climate with abundant precipitation, recording 1192 mm of rainfall per year.

Monthly Precipitation Levels

The average number of days each month with precipitation (> 0.2 mm)

San Juan can be quite wet during September, receiving approximately 159 mm of precipitation over 18 rainy days.

In contrast February, experiences much drier conditions, with 47 mm of rainfall, spread across 15 rainy days.

September, the city’s wettest month, has a maximum daytime temperature of 31°C and receives 236 hours of sunshine. During the driest month February you can expect a temperature of 28°C. For more detailed insights into the city’s temperatures, visit our San Juan Temperature page.

Annual Precipitation in Puerto Rico

The map below shows the annual precipitation across Puerto Rico. You can also select the different months in case you are interested in a specific month.

Amsterdam Precipitation Compared World Wide

San Juan’s average annual precipitation is 1192 mm. Let’s compare this to some popular worldwide tourist destinations:

The climate in San Francisco, USA, is influenced by coastal weather, with 469 mm of rainfall mostly during the winter months.

Osaka, Japan, experiences 1507 mm of rainfall annually, spread across the year with wetter summers.

Melbourne, Australia, has 690 mm of rainfall annually, spread fairly evenly throughout the year.

Kuala Lumpur, Malaysia, receives 2529 mm of annual rainfall, characteristic of its equatorial tropical rainforest climate, with consistent rainfall throughout the year and peak months during March and November.

How is Precipitation Measured?

Precipitation amounts are measured using specific gauges installed at weather stations, collecting both rain and snow and any other type of precipitation. Rainfall is measured directly in millimeters, while that from snow and ice is obtained by melting it. Automated systems often incorporate heaters to make this easier.

Information from these stations is transmitted via Wi-Fi, satellite, GPS, or telephone connections to central monitoring networks. This information is immediately updated and integrated into weather models and forecasts.

Interesting weather facts

• Mawsynram in India is noted as being the wettest place on earth, with over 11 meters of rain falling every year.
• In contrast, Antofagasta in Chile is among the driest places on the planet, getting less than 0.1mm per year, with some years recording virtually no rainfall.
• Nearly 1,650 thunderstorm cells are estimated over the planet at any given time.

For more detailed information about San Juan’s weather, including sunshine hours, humidity levels, and temperature data, visit our San Juan Climate page.