Rialto (CA) Temperature by Month

Rialto, California, United States of America has an average annual maximum temperature of 26°C (79°F), ranging from 18°C (64°F) in December to 35°C (95°F) in August. Below you'll find a full monthly breakdown and a comparison with cities worldwide.

Depending on the time of the year, temperatures range from very warm to pleasant in Rialto. At night, minimum temperatures range from 18°C (64°F) in August to 6°C (43°F) in December.

The chart below illustrates the average maximum day and minimum night temperatures in Rialto by month:

From around 4 AM to 6 AM temperatures are at their lowest; by 3 PM they've climbed to their daily peak. August, the warmest month, averages 351 hours of sunshine.

The chart below shows the average temperature throughout the year:

Rialto's average annual maximum temperature is 26°C (79°F). To put that in context, here's how it compares to a few well-known destinations:

Barcelona, Spain has an annual average of around 21°C (70°F), with warm summers and mild, fairly short winters.

Glasgow, Scotland averages 13°C (55°F) a year, mild but often grey, with cold winters and rarely hot summers.

Osaka, Japan averages 22°C (72°F) annually, with hot humid summers, mild winters, and pleasant spring and autumn seasons.

Brisbane, Australia averages 26°C (79°F) a year, with warm winters and hot, humid summers.

Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.

The readings come from a range of sources, land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.

Global average temperatures have risen by around 1.2°C since the pre-industrial era, and the effects are visible across many regions. Winters are milder on average, with fewer frost days and less snow in many parts of the world. Heatwaves are more frequent and more intense, and Europe's summers of 2018, 2019, and 2020 all set records.

Summers are also getting drier in some areas, while winter rainfall has increased in others. This contributies to higher river levels and more flooding. In many countries, spring arrives earlier and autumn lasts longer. It has knock-on effects for wildlife, agriculture, and local ecosystems.

For more on Rialto's weather, including monthly rainfall, sunshine hours, and humidity, visit our Rialto climate page.