Cornwall (ON) Temperature by Month
Cornwall in Ontario, Canada sees significant seasonal temperature differences, with daytime highs between -4°C (25°F) in January and 27°C (81°F) in July, averaging 12°C (54°F) annually. Explore the full monthly breakdown below.
Cornwall Monthly Temperatures
With significant temperature fluctuations, Cornwall enjoys distinct seasons year-round. Nighttime lows range from 16°C (61°F) in July to -12°C (10°F) in January.
The chart below illustrates the average maximum day and minimum night temperatures in Cornwall by month:
From around 4 AM to 6 AM temperatures are at their lowest; by 3 PM they've climbed to their daily peak.
The chart below shows the average temperature throughout the year:
Temperature: Cornwall vs Canada
The map below shows the annual temperature across Canada. You can also select individual months if you want to compare a specific time of year.
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Cornwall vs World: Temperature Compared
Cornwall's average annual maximum temperature is 12°C (54°F). To put that in context, here's how it compares to a few well-known destinations:
Athens, Greece sits at 23°C (73°F) on average, with hot dry summers and mild winters characteristic of the Mediterranean.
Zermatt, Switzerland averages just 4°C (39°F) annually due to its altitude, with very cold winters and cool summers even at its warmest.
Osaka, Japan averages 22°C (72°F) annually, with hot humid summers, mild winters, and pleasant spring and autumn seasons.
Perth, Australia averages 25°C (77°F) annually, with a classic Mediterranean climate — hot dry summers and mild wet winters.
Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.
The readings come from a range of sources — land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.
Seasonal temperature shifts influence more than just how warm it feels — they also drive changes in rainfall, cloud cover, and wind patterns throughout the year.
Warmer air holds more moisture, which tends to mean heavier or more frequent rain during the warmer months. When temperatures drop in winter, any precipitation that does fall is more likely to come as snow or sleet, though in Cornwall this rarely lasts long on the ground.
For more on Cornwall's weather — including monthly rainfall, sunshine hours, and humidity — visit our Cornwall climate page.
