2025 Compare Climate & Weather:
Ontario, CA vs San Diego, CA

Highlights

On average, there are 266 sunny days per year in San Diego. Ontario averages 279 sunny days per year. The US average is 205 sunny days.

San Diego, California gets 11.7 inches of rain, on average, per year. Ontario, California gets 15.7 inches of rain, on average, per year. The US average is 38.1 inches of rain per year.

San Diego averages 0 inches of snow per year. Ontario averages 0 inches of snow per year. The US average is 27.8 inches of snow per year.

Weather Highlights

San Diego, California
Summer High: the July high is around 78.5 degrees
Winter Low: the January low is 45.6
Rain: averages 11.7 inches of rain a year
Snow: averages 0 inches of snow a year

Ontario, California
Summer High: the July high is around 91.9 degrees
Winter Low: the January low is 42.6
Rain: averages 15.7 inches of rain a year
Snow: averages 0 inches of snow a year

BestPlaces Comfort Index

The annual BestPlaces Comfort Index for San Diego is 9.2 (10=best), which means it is one of the most pleasant places in California.

The annual BestPlaces Comfort Index for Ontario is 8.8 (10=best), which means it is more comfortable than most places in California.

Today's Weather - Ontario, CA

59°F

Today's Weather - San Diego, CA

57°F

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: Ontario / San Diego

August is the hottest month for Ontario with an average high temperature of 93.4°, which ranks it as warmer than most places in California. In Ontario, there are 5 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Ontario are May, October and April.

August is the hottest month for San Diego with an average high temperature of 80.2°, which ranks it as cooler than most places in California. In San Diego, there are 7 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for San Diego are July, September and August.

December has the coldest nighttime temperatures for Ontario with an average of 41.4°. This is warmer than most places in California.

December has the coldest nighttime temperatures for San Diego with an average of 45.3°. This is one of the warmest places in California.

In Ontario, there are 79.5 days annually when the high temperature is over 90°, which is hotter than most places in California.

In San Diego, there are 13.4 days annually when the high temperature is over 90°, which is cooler than most places in California.

In Ontario, there are 3.6 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in California.

In San Diego, there are 0.7 days annually when the nighttime low temperature falls below freezing, which is one of the warmest places in California.

In Ontario, there are 0.0 days annually when the nighttime low temperature falls below zero°, which is about average compared to other places in California.

In San Diego, there are 0.0 days annually when the nighttime low temperature falls below zero°, which is about average compared to other places in California.

February is the wettest month in Ontario with 3.8 inches of rain, and the driest month is July with 0.0 inches. The wettest season is Spring with 60% of yearly precipitation and 1% occurs in Autumn, which is the driest season. The annual rainfall of 15.7 inches in Ontario means that it is drier than most places in California.


February is the wettest month in San Diego with 2.5 inches of rain, and the driest month is August with 0.0 inches. The wettest season is Spring with 55% of yearly precipitation and 2% occurs in Autumn, which is the driest season. The annual rainfall of 11.7 inches in San Diego means that it is drier than most places in California.

February is the rainiest month in Ontario with 5.7 days of rain, and July is the driest month with only 0.2 rainy days. There are 30.5 rainy days annually in Ontario, which is one of the least rainy places in California. The rainiest season is Spring when it rains 50% of the time and the driest is Autumn with only a 4% chance of a rainy day.

February is the rainiest month in San Diego with 6.8 days of rain, and August is the driest month with only 0.4 rainy days. There are 38.4 rainy days annually in San Diego, which is less rainy than most places in California. The rainiest season is Spring when it rains 48% of the time and the driest is Autumn with only a 4% chance of a rainy day.

There is rarely any recorded snowfall in Ontario, ranking it as one of the least snowy places in California.

There is rarely any recorded snowfall in San Diego, ranking it as one of the least snowy places in California.

Any measurable snowfall is a rare occurance in Ontario.

Any measurable snowfall is a rare occurance in San Diego.