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May Weather in Ottawa, United States

Last updated: June 24, 2025

In May, the average temperature in Ottawa, United States hovers around 17°C (63°F). However, be prepared for a range, as the minimum can dip to -1°C (30°F) while highs may soar to 34°C (94°F). Expect approximately 134 mm (5.3 in) of precipitation over 15 days, accompanied by an average humidity level of 81%.

May Temperature in Ottawa

In May in Ottawa, the average temperature is 17°C (63°F), with maximums reaching 34°C (94°F) and minimums dropping as low as -1°C (30°F). This variation makes it an ideal time for travelers to pack both light clothing for warm days and warmer layers for chilly nights.

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

The chart illustrates May 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, May typically has an average temperature of 17°C (63°F), with highs reaching up to 34°C (94°F) and lows dropping to around -1°C (30°F).
JanFebMarAprMayJunJulAugSepOctNovDec293141506372767368574135
Data source: Temperature data for Ottawa generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

May Precipitation in Ottawa

In Ottawa in May, the total precipitation amount is 134 mm (5.3 in) spread over a period of 15 days.

May Precipitation Trends in Ottawa

The chart displays monthly precipitation patterns in Ottawa, with values for each month alongside May’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how May’s conditions compare to those of other months. In Ottawa, May typically receives around 134 mm (5.3 inches) of precipitation spread over approximately 15 days.
JanFebMarAprMayJunJulAugSepOctNovDec738395991341221108870918562
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in Ottawa

In Ottawa in May humidity is 81%. With an average temperature of 17°C (63°F), this humidity feels like a warm blanket enveloping you, making travel slightly oppressive and calling for frequent breaks in air-conditioned spaces to recharge and enjoy your journey comfortably.

May Average Humidity in Ottawa

This chart illustrates the average monthly humidity levels in Ottawa, with May’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In May, average humidity in Ottawa is approximately 81%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec88%87%87%88%81%82%81%78%78%82%89%86%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in Ottawa

In Ottawa in May, 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 Ottawa.

Maximum UV Index Levels in Ottawa for May

The chart shows the monthly maximum UV Index (UVI) for Ottawa in May, 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 May, the maximum UV index in Ottawa typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910101098642
Data source: Ottawa May 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 May 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 May’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 May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-2°C (29°F)73 mm (2.9 inches)88%moderate
February Weather0°C (32°F)83 mm (3.3 inches)87%moderate
March Weather5°C (41°F)95 mm (3.8 inches)87%high
April Weather10°C (50°F)99 mm (3.9 inches)87%very high
May Weather17°C (63°F)134 mm (5.3 inches)81%very high
June Weather22°C (72°F)122 mm (4.8 inches)82%very high
July Weather24°C (76°F)110 mm (4.3 inches)81%very high
August Weather23°C (73°F)88 mm (3.4 inches)78%very high
September Weather20°C (68°F)70 mm (2.8 inches)78%very high
October Weather14°C (57°F)91 mm (3.6 inches)82%high
November Weather5°C (42°F)85 mm (3.3 inches)89%moderate
December Weather2°C (35°F)62 mm (2.5 inches)86%low

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