San Sebastian Monthly Rainfall & Precipitation

This page shows both the average monthly rainfall and the number of rainy days in San Sebastian, Puerto Rico. The figures are based on a 30-year period (1990–2020) to provide a reliable average. Let's now guide you through the details for a complete overview.

San Sebastian has a relatively rainy climate with high precipitation levels, averaging 1086 mm (43 in) of rainfall annually. Despite the high annual total, it does experience a distinct dry season during certain months. Examine our detailed charts below to understand these seasonal patterns.

Monthly Precipitation Levels

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

Significant seasonal changes in precipitation occur throughout the year. During the wettest month, September receives substantial rainfall, averaging 158 mm (6.2 in) of precipitation, recorded across 17 rainy days.

In contrast, the driest month, January brings less rainfall, with 34 mm (1.3 in) over 19 rainy days.

September, the wettest month, has a maximum daytime temperature of 31°C (88°F). During the driest month January you can expect a temperature of 29°C (84°F). For more detailed insights into the city's temperatures, visit our San Sebastian Temperature page.

San Sebastian's average annual precipitation is 1086 mm (43 in). Let's compare this to some popular worldwide tourist destinations:

Chicago, USA, sees an annual precipitation of 1062 mm (42 in), with rain and snow contributing to its humid climate.

In Shanghai, China, the annual average precipitation is 1347 mm (53 in), with a humid subtropical climate.

In Tokyo, Japan, the average annual precipitation is 1528 mm (60 in), with significant summer rains due to typhoon season.

Mumbai, India, experiences a tropical monsoon climate with 1860 mm (73 in) of annual rainfall, with the majority of precipitation happening during the monsoon season from June to September.

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 Sebastian's weather, including sunshine hours, humidity levels, and temperature data, visit our San Sebastian Climate page.