Hyperlocal rainfall totals + real-time NOAA forecasts
Accurate weather without the clutter
Ontario, CA Weather by Month and Climate Averages
Monthly normals · Rain · Snow
Sunshine · Freeze dates · Records · Best time to visit
What is the weather like in Ontario, CA?
Ontario, CA gets 11.6 in of precipitation a year over about 35 rainy days. August is the warmest month (average high 94°F) and December the coldest (average low 43°F).
Semi-arid climate
Ontario, CA has hot summers and mild winters. Daytime highs range from about 67°F in December to 94°F in August. February is usually the wettest month. The most comfortable time to visit is typically January, March to May, and November to December, when daytime highs sit near 72°F.
| Season | Months | Avg low | Avg high |
|---|---|---|---|
| Winter | Dec–Feb | 44° | 67° |
| Spring | Mar–May | 52° | 75° |
| Summer | Jun–Aug | 63° | 91° |
| Autumn | Sep–Nov | 56° | 82° |
How much rain does Ontario get?
Ontario gets 11.6 in of precipitation in an average year, spread over about 35 days with measurable rain. That is fewer rainy days than 90% of the US.
February is the wettest month, with 3.1 in. June is the driest, with 0.0 in. February has the most rainy days, about 6.
The longest dry spell in the last five years lasted 175 days, to October 27, 2024.
From September 2025 to August 2026 Ontario got 15.3 in of rain, against a normal of 11.6 in for those months. February 2026 had the most, with 4.1 in.
See where Ontario ranks: rainiest cities in the US, US cities with the most rainy days, rainiest cities in California.
Ontario weather by month
Ontario weather in January
In January, Ontario averages a high of 68°F and a low of 44°F. It gets 2.6 in of precipitation over about 5 rainy days. Estimated sunshine is 54% of daylight hours, derived from ERA5 cloud cover. The January record high is 90°F (2003) and the record low is 25°F (2007). January is one of the most comfortable months to visit.
Ontario weather in February
In February, Ontario averages a high of 67°F and a low of 45°F. It gets 3.1 in of precipitation over about 6 rainy days. Estimated sunshine is 61% of daylight hours, derived from ERA5 cloud cover. The February record high is 91°F (2026) and the record low is 29°F (2018).
Ontario weather in March
In March, Ontario averages a high of 71°F and a low of 48°F. It gets 1.6 in of precipitation over about 5 rainy days. Estimated sunshine is 50% of daylight hours, derived from ERA5 cloud cover. The March record high is 100°F (2026) and the record low is 33°F (2023). March is one of the most comfortable months to visit.
Ontario weather in April
In April, Ontario averages a high of 75°F and a low of 51°F. It gets 0.8 in of precipitation over about 4 rainy days. Estimated sunshine is 60% of daylight hours, derived from ERA5 cloud cover. The April record high is 101°F (2004) and the record low is 33°F (1999). April is one of the most comfortable months to visit.
Ontario weather in May
In May, Ontario averages a high of 79°F and a low of 56°F. It gets 0.3 in of precipitation over about 2 rainy days. Estimated sunshine is 65% of daylight hours, derived from ERA5 cloud cover. The May record high is 103°F (2004) and the record low is 42°F (1999). May is one of the most comfortable months to visit.
Ontario weather in June
In June, Ontario averages a high of 86°F and a low of 60°F. It gets 0.0 in of precipitation over about 0 rainy days. Estimated sunshine is 73% of daylight hours, derived from ERA5 cloud cover. The June record high is 112°F (2016) and the record low is 46°F (1999).
Ontario weather in July
In July, Ontario averages a high of 93°F and a low of 65°F. It gets 0.1 in of precipitation over about 1 rainy days. Estimated sunshine is 84% of daylight hours, derived from ERA5 cloud cover. The July record high is 117°F (2018) and the record low is 56°F (2004).
Ontario weather in August
In August, Ontario averages a high of 94°F and a low of 65°F. It gets 0.0 in of precipitation over about 0 rainy days. Estimated sunshine is 83% of daylight hours, derived from ERA5 cloud cover. The August record high is 112°F (2017) and the record low is 56°F (1999).
Ontario weather in September
In September, Ontario averages a high of 91°F and a low of 63°F. It gets 0.1 in of precipitation over about 1 rainy days. Estimated sunshine is 79% of daylight hours, derived from ERA5 cloud cover. The September record high is 118°F (2020) and the record low is 51°F (2013).
Ontario weather in October
In October, Ontario averages a high of 82°F and a low of 57°F. It gets 0.4 in of precipitation over about 2 rainy days. Estimated sunshine is 75% of daylight hours, derived from ERA5 cloud cover. The October record high is 107°F (2012) and the record low is 41°F (2019).
Ontario weather in November
In November, Ontario averages a high of 74°F and a low of 49°F. It gets 0.8 in of precipitation over about 4 rainy days. Estimated sunshine is 69% of daylight hours, derived from ERA5 cloud cover. The November record high is 98°F (2010) and the record low is 32°F (2015). November is one of the most comfortable months to visit.
Ontario weather in December
In December, Ontario averages a high of 67°F and a low of 43°F. It gets 1.9 in of precipitation over about 6 rainy days. Estimated sunshine is 51% of daylight hours, derived from ERA5 cloud cover. The December record high is 87°F (2021) and the record low is 28°F (1998). December is one of the most comfortable months to visit.
Sunshine, humidity and wind in Ontario
July is the sunniest month in Ontario, with estimated sunshine of 84% of daylight hours from ERA5 cloud cover. March is the cloudiest, at 50%. The annual cloud-cover estimate is 67% of daylight hours; it is not a measurement of sunshine duration. Ontario is sunnier than 94% of the US.
Humidity peaks in May at 63% and is lowest in November at 37%.
Wind averages 6 mph over the year, and May is the windiest month at 7 mph.
Ontario has about 92 days a year above 90°F. Ontario is hotter than 90% of the US.
Thunderstorms occur on about 6 days a year.
See where Ontario ranks: sunniest cities in the US, cloudiest cities in the US, hottest cities in the US.
Ontario weather records
These records cover ONTARIO INTL AP during 1998–2026. Earlier records or other stations in the city may differ.
The hottest temperature on record at the Ontario station is 118°F, on September 5, 2020. The coldest is 25°F, on January 14, 2007.
The wettest day in the available station history brought 3.6 in of precipitation, on February 5, 2024.
The best time to visit Ontario
The most comfortable time to visit is typically January, March to May, and November to December, when daytime highs sit near 72°F.
Winter (December–February) is mild, with average highs around 67°F and lows near 44°F.
Spring (March–May) is warm, with average highs around 75°F and lows near 52°F.
Summer (June–August) is hot, with average highs around 91°F and lows near 63°F.
Autumn (September–November) is hot, with average highs around 82°F and lows near 56°F.
Monthly climate
| Month | Average low | Average high | Precip | Rain days | Wind | Humidity | Estimated sunshine | Record high | Record low |
|---|---|---|---|---|---|---|---|---|---|
| January | 44° | 68° | 2.6 in | 5 | 5 mph | 52% | 54% | 90° | 25° |
| February | 45° | 67° | 3.1 in | 6 | 5 mph | 45% | 61% | 91° | 29° |
| March | 48° | 71° | 1.6 in | 5 | 6 mph | 59% | 50% | 100° | 33° |
| April | 51° | 75° | 0.76 in | 4 | 7 mph | 60% | 60% | 101° | 33° |
| May | 56° | 79° | 0.30 in | 2 | 7 mph | 63% | 65% | 103° | 42° |
| June | 60° | 86° | 0.02 in | 0 | 7 mph | 58% | 73% | 112° | 46° |
| July | 65° | 93° | 0.05 in | 1 | 7 mph | 53% | 84% | 117° | 56° |
| August | 65° | 94° | 0.03 in | 0 | 6 mph | 52% | 83% | 112° | 56° |
| September | 63° | 91° | 0.10 in | 1 | 6 mph | 52% | 79% | 118° | 51° |
| October | 57° | 82° | 0.41 in | 2 | 5 mph | 46% | 75% | 107° | 41° |
| November | 49° | 74° | 0.80 in | 4 | 5 mph | 37% | 69% | 98° | 32° |
| December | 43° | 67° | 1.9 in | 6 | 5 mph | 47% | 51% | 87° | 28° |
Station: ONTARIO INTL AP, 7 km from the city. Temperature normal baseline: 1991–2020, calculated from available NOAA GHCN-Daily observations. Available station history: 1998–2026; record values refer to this station and period, not the entire city’s history. Precipitation includes rain and the water equivalent of frozen precipitation; snowfall depth is shown separately when available. Sources and methods
From ERA5 reanalysis. Sunshine is estimated from cloud cover.
Ontario climate questions
How much rain does Ontario get?
Ontario gets 11.6 in of precipitation in an average year, over about 35 rainy days.
What is the wettest month in Ontario?
February is the wettest month in Ontario, with 3.1 in. June is the driest, with 0.0 in.
How many rainy days does Ontario have a year?
Ontario has about 35 days with measurable rain in an average year. February has the most, about 6.
What is the hottest month in Ontario?
August is the warmest month in Ontario, with an average high of 94°F.
What is the coldest month in Ontario?
December is the coldest month in Ontario, with an average low of 43°F.
What is the record high temperature in Ontario?
Within the available 1998–2026 station history, the record high at the Ontario station is 118°F, set on September 5, 2020. The record low is 25°F, on January 14, 2007.
What is the sunniest month in Ontario?
July is the sunniest month in Ontario, with estimated sunshine of 84% of daylight hours from ERA5 cloud cover. March is the cloudiest.
What is the best time to visit Ontario?
The most comfortable time to visit is typically January, March to May, and November to December, when daytime highs sit near 72°F.