August Weather in Ontario, United States

Last updated: June 24, 2025

In August, the average temperature in Ontario, United States hovers around 25°C (77°F). Temperatures can range from a cool 15°C (60°F) to a scorching 39°C (102°F). With only 2 mm (0.1 in) of precipitation over 0 days and an average humidity of 69%, it’s a great time to enjoy the warm, dry weather!

August Temperature in Ontario

In August in Ontario, the average temperature is 25°C (77°F). Maximum temperatures can reach 39°C (102°F), while minimums can drop to as low as 15°C (60°F). This variability makes Ontario an ideal destination for travelers who enjoy warm weather but also appreciate cooler evenings.

August Weather in Ontario: Daily Temperature Highs, Lows, and Averages

The chart illustrates August temperature patterns in Ontario, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Ontario, August typically has an average temperature of 25°C (77°F), with highs reaching up to 39°C (102°F) and lows dropping to around 15°C (60°F).

Data source: Temperature data for Ontario generated using information from the Copernicus Climate Change Service.

August Precipitation in Ontario

In Ontario in August, the precipitation amount is 2 mm (0.1 in) during a span of 0 days.

August Precipitation Trends in Ontario

The chart displays monthly precipitation patterns in Ontario, with values for each month alongside August’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how August’s conditions compare to those of other months. In Ontario, August typically receives around 2 mm (0.1 inches) of precipitation spread over approximately 0 days.

Data source: Precipitation data for August generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

August Humidity in Ontario

In Ontario in August humidity is 69%. With an average temperature of 25°C (77°F), this humidity feels like a warm, heavy blanket enveloping you, making every step feel slightly sluggish and encouraging frequent breaks to enjoy refreshing beverages and cool breezes.

August Average Humidity in Ontario

This chart illustrates the average monthly humidity levels in Ontario, with August’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In August, average humidity in Ontario is approximately 69%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for August generated using information from the Copernicus Climate Change Service.

August UV Index in Ontario

In Ontario in August, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Ontario.

Maximum UV Index Levels in Ontario for August

The chart shows the monthly maximum UV Index (UVI) for Ontario in August, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In August, the maximum UV index in Ontario typically reaches 10, which falls under the very high exposure category.

Data source: Ontario August UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How August Weather in Ontario Compares to Other Months

Weather in Ontario varies notably across the year, with each month offering distinct climate conditions. This page compares August’s weather to other months in Ontario, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Ontario, showing how August’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	12°C (54°F)	80 mm (3.1 inches)	74%	moderate
February Weather	12°C (55°F)	70 mm (2.8 inches)	79%	high
March Weather	14°C (57°F)	76 mm (3.0 inches)	75%	very high
April Weather	16°C (62°F)	27 mm (1.1 inches)	70%	very high
May Weather	18°C (64°F)	17 mm (0.7 inches)	70%	very high
June Weather	21°C (70°F)	1 mm (0.0 inches)	72%	extreme
July Weather	24°C (76°F)	1 mm (0.1 inches)	73%	extreme
August Weather	25°C (77°F)	2 mm (0.1 inches)	69%	very high
September Weather	23°C (74°F)	3 mm (0.1 inches)	68%	very high
October Weather	20°C (68°F)	12 mm (0.5 inches)	67%	high
November Weather	16°C (61°F)	26 mm (1.0 inches)	68%	moderate
December Weather	12°C (54°F)	79 mm (3.1 inches)	71%	moderate