Ontario, CA Weather & Climate Normals
Ontario's real weather, in one number
Ontario, CA scores 75/100 on this site's reading of NOAA's own 30-year normals: mild with real seasons. A solid stretch of comfortable months alongside a noticeable but not extreme summer or winter. 9 of the year's 12 months average between 55 and 75°F, the range this site counts as mild.
Ontario's hottest and coldest months
Ontario's hottest month is Aug, averaging 80°F; its coldest is Dec, averaging 55°F, a 24.8°F swing across the year, a middling gap by national standards.
Rain and snow in Ontario
Over a typical year, Ontario sees about 11.64in of precipitation a year across roughly 36 days with measurable rain or snow. That station has no snowfall reading, so none is shown rather than assumed.
Where Ontario ranks
Ontario ranks 213 of 4876 US cities in this dataset for comfort score, and 213 of 429 within CA. About 185,285 people live there.
If you need tomorrow's forecast, not the 30-year average
Everything above is a 30-year average from ONTARIO INTL AP, CA US, 1.4 miles from Ontario, not a prediction for any specific day.
More on how this is worked out
Why some cities show no snow or rain figure · How the comfort score is calculated