Saint Marys (ON) Temperature by Month
Saint Marys, Ontario, Canada has an average annual maximum temperature of 14°C (57°F), ranging from -1°C (30°F) in January to 27°C (81°F) in July. Below you'll find a full monthly breakdown and a comparison with cities worldwide.
Saint Marys Monthly Temperatures
The climate in Saint Marys is dynamic, ranging widely from very cold in winter to comfortable in summer. Nights are significantly colder, with lows dropping from 15°C (59°F) in July to -10°C (14°F) in January.
The chart below illustrates the average maximum day and minimum night temperatures in Saint Marys 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: Saint Marys 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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Saint Marys vs World: Temperature Compared
Saint Marys's average annual maximum temperature is 14°C (57°F). To put that in context, here's how it compares to a few well-known destinations:
Lisbon, Portugal averages 21°C (70°F) annually — warm summers, mild winters, and rain mainly in the cooler months.
Interlaken, Switzerland averages 8°C (46°F) a year, with cold winters and cool summers thanks to its Alpine setting.
Seoul, South Korea averages 18°C (64°F) a year, with four clear seasons, cold winters, and hot humid summers.
Melbourne, Australia averages 20°C (68°F) annually — known for unpredictable weather, with four seasons sometimes happening in one day.
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.
For cities and regions with significant elevation, altitude is one of the biggest factors shaping local temperatures. As a rule of thumb, temperatures fall by around 6°C for every 1,000 metres gained — so a city at 2,000 metres will typically be around 12°C cooler than a city at sea level in the same region. Higher ground also tends to see more dramatic day-to-night temperature swings, since thinner air loses heat faster after sunset.
For more on Saint Marys's weather — including monthly rainfall, sunshine hours, and humidity — visit our Saint Marys climate page.
