August Weather in Ottawa, United States

Last updated: June 24, 2025

In Ottawa, United States, the average temperature in August hovers around 23°C (73°F), making it a pleasant time to visit. Temperature fluctuations can be notable, with a minimum dipping to 9°C (48°F) and a maximum soaring to 34°C (93°F). Expect some rain as well, with an average precipitation of 88 mm (3.4 in) spread over 11 days. Alongside this, the average humidity remains at a comfortable 78%.

August Temperature in Ottawa

In August in Ottawa, the average temperature is 23°C (73°F), with maximums reaching up to 34°C (93°F) and minimums dropping as low as 9°C (48°F). It's a great time for travelers to enjoy pleasant weather while exploring the rich offerings of Ottawa.

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

The chart illustrates August temperature patterns in Ottawa, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Ottawa, August typically has an average temperature of 23°C (73°F), with highs reaching up to 34°C (93°F) and lows dropping to around 9°C (48°F).

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

August Precipitation in Ottawa

In Ottawa in August, the precipitation amount is 88 mm (3.4 in) during 11 days, indicating a relatively wet period for the area.

August Precipitation Trends in Ottawa

The chart displays monthly precipitation patterns in Ottawa, 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 Ottawa, August typically receives around 88 mm (3.4 inches) of precipitation spread over approximately 11 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 Ottawa

In Ottawa in August, humidity is 78%. With an average temperature of 23°C (73°F), this humidity feels like a warm, sticky embrace, making outdoor activities a little challenging but still enjoyable for travelers who appreciate a tropical atmosphere.

August Average Humidity in Ottawa

This chart illustrates the average monthly humidity levels in Ottawa, 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 Ottawa is approximately 78%, 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 Ottawa

In Ottawa in August, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Ottawa.

Maximum UV Index Levels in Ottawa for August

The chart shows the monthly maximum UV Index (UVI) for Ottawa 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 Ottawa typically reaches 9, which falls under the very high exposure category.

Data source: Ottawa 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 Ottawa Compares to Other Months

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

This table compares monthly weather conditions in Ottawa, showing how August’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-2°C (29°F)	73 mm (2.9 inches)	88%	moderate
February Weather	0°C (32°F)	83 mm (3.3 inches)	87%	moderate
March Weather	5°C (41°F)	95 mm (3.8 inches)	87%	high
April Weather	10°C (50°F)	99 mm (3.9 inches)	87%	very high
May Weather	17°C (63°F)	134 mm (5.3 inches)	81%	very high
June Weather	22°C (72°F)	122 mm (4.8 inches)	82%	very high
July Weather	24°C (76°F)	110 mm (4.3 inches)	81%	very high
August Weather	23°C (73°F)	88 mm (3.4 inches)	78%	very high
September Weather	20°C (68°F)	70 mm (2.8 inches)	78%	very high
October Weather	14°C (57°F)	91 mm (3.6 inches)	82%	high
November Weather	5°C (42°F)	85 mm (3.3 inches)	89%	moderate
December Weather	2°C (35°F)	62 mm (2.5 inches)	86%	low