San Mateo (CA) Rainfall & Precipitation: Monthly Averages and Year-Round Insights

This page shows the average amount of rainfall per month in San Mateo (CA). The numbers are calculated over a 30-year period to provide a reliable average. Now, let’s break down all the details for a clearer picture.

San Mateo typically sees modest rainfall throughout the year, with an average annual precipitation of 415 mm.

Monthly Precipitation Levels

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

Significant seasonal changes in precipitation occur throughout the year. During the wet season, December receives substantial rainfall, averaging 99 mm of precipitation, recorded across 13 rainy days.

In contrast, the drier season, July brings less rainfall, with 0 mm over 0 rainy days.

December, the city’s wettest month, has a maximum daytime temperature of 15°C and receives 160 hours of sunshine. During the driest month July you can expect a temperature of 24°C. For more detailed insights into the city’s temperatures, visit our San Mateo Temperature page.

Annual Precipitation in the United States of America

The map below shows the annual precipitation across the United States of America. You can also select the different months in case you are interested in a specific month.

Amsterdam Precipitation Compared World Wide

San Mateo’s average annual precipitation is 415 mm. Let’s compare this to some popular worldwide tourist destinations:

The city of Rome, Italy, has an average annual precipitation of 832 mm, spread fairly evenly throughout the year.

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

Adelaide, Australia, enjoys 511 mm of annual precipitation, with dry summers and wet winters.

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

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.

Sea vs. Land Precipitation

The proximity of a location to a large body of water can significantly affect its rainfall patterns:

• Ocean Influence: Coastal regions typically receive more rainfall due to the presence of moisture-laden winds from the ocean. These regions tend to have more humid climates and experience more frequent precipitation, especially in winter.
• Continental Climates: Areas further from the sea, such as inland or continental regions, experience less frequent rainfall and more extreme seasonal variations in precipitation.

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