San Juan Monthly Rainfall & Precipitation

This page shows both the average monthly rainfall and the number of rainy days in San Juan, Luzon, Philippines. This average is based on long-term data collected between 1990 and 2020. Let's explore the details to provide you with a complete overview.

San Juan experiences significant rainfall throughout the year, averaging 3106 mm (122 in) of precipitation annually. However, this abundant rainfall is not evenly distributed, with a distinct rainy season during certain months. You can clearly see this in our monthly precipitation graphs below.

Monthly Precipitation Levels

The average number of days each month with precipitation (> 0.2 mm (0.01 in))

The climate in San Juan shows significant variation throughout the year. Expect 644 mm (25 in) of precipitation during the wettest month August, distributed over 23 rainy days.

In contrast, January offers drier and sunnier days, with around 58 mm (2.3 in) of rainfall over a single rainy day.

August, the wettest month, has a maximum daytime temperature of 29°C (84°F). During the driest month January you can expect a temperature of 28°C (82°F). For more detailed insights into the city's temperatures, visit our San Juan Temperature page.

San Juan's average annual precipitation is 3106 mm (122 in). Let's compare this to some popular worldwide tourist destinations:

In Lisbon, Portugal, the average annual precipitation is 774 mm (30 in), characterized by wet winters and dry summers typical of the Mediterranean climate.

Osaka, Japan, experiences 1507 mm (59 in) of rainfall annually, spread across the year with wetter summers.

Perth, Australia, receives 565 mm (22 in) of rainfall annually, mostly during the winter months.

Ho Chi Minh City, Vietnam, receives 1955 mm (77 in) of annual rainfall, with a pronounced wet season from May to November, typical of its tropical monsoon climate.

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.

Precipitation has a very strong role in determining the local climate and ecosystem:

• Changing Rainfall Patterns: Global warming causes drastic changes in the patterns of rainfall. Some areas have been experiencing increased frequency and intensity of rainfall, while other areas experience longer dry spells or even droughts.
• Local Impacts: Many regions are experiencing heavier rainfall in the winter months and drier, hotter summers. This affects agriculture, water resources, and ecosystems.

• Mawsynram in India is noted as being the wettest place on earth, with over 11 meters (36 feet) of rain falling every year.
• In contrast, Antofagasta in Chile is among the driest places on the planet, getting less than 0.1mm (0.004 inches) 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.