Ontario, CA Weather by Month and Climate Averages

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.

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. The sun is out about 54% of daylight hours. 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. The sun is out about 61% of daylight hours. 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. The sun is out about 50% of daylight hours. 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. The sun is out about 60% of daylight hours. 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. The sun is out about 65% of daylight hours. 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. The sun is out about 73% of daylight hours. 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. The sun is out about 84% of daylight hours. 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. The sun is out about 83% of daylight hours. 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. The sun is out about 79% of daylight hours. 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. The sun is out about 75% of daylight hours. 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. The sun is out about 69% of daylight hours. 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. The sun is out about 51% of daylight hours. 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 sunshine about 84% of daylight hours. March is the cloudiest, at 50%. Over the year the sun shines about 67% of daylight hours. 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

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 on record brought 3.6 in of rain, 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.

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?

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 sunshine about 84% of daylight hours. 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.