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

This page shows the average amount of rainfall per month in Ontario (CA). The numbers are calculated over a 30-year period to provide a reliable average. Now, let’s explore all the details to give you a full picture.

Ontario typically sees modest rainfall throughout the year, with an average annual precipitation of 273 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 78 mm of precipitation, recorded across 8 rainy days.

In contrast, the drier season, June brings less rainfall, with 0.1 mm over 0 rainy days.

December, the city’s wettest month, has a maximum daytime temperature of 19°C and receives 205 hours of sunshine. During the driest month June you can expect a temperature of 30°C. For more detailed insights into the city’s temperatures, visit our Ontario 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

Ontario’s average annual precipitation is 273 mm. Let’s compare this to some popular worldwide tourist destinations:

Athens, Greece, receives an average annual precipitation of 400 mm, making it one of the drier Mediterranean climates with rainfall mostly in winter.

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

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

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

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

• The U.S. has a significant number of thunderstorms every year, with over 14.6 million taking place across the world annually.
• Approximately 70% of lightning bolts strike land rather than oceans.
• A storm named John was the longest-lasting Pacific tropical storm, continuing for 31 days. As it crossed the dateline twice, it changed status from a hurricane to a typhoon and back to a hurricane.

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