St. Thomas has a temperate climate with warm summers and freezing winters.
Temperatures peak in July and drop to their lowest in January, while rainfall is highest during autumn months.
Humidity remains high throughout the year, especially during winter months, creating cold and damp conditions.
| Month | 🌤️ | Avg High | Avg Temp | Avg Low | Record High | Record Low | Humid % | Rain (mm) | Wind (m/s) | Solar (kWh/m²) |
|---|---|---|---|---|---|---|---|---|---|---|
| January | ❄️ | -2.0°C | -5.2°C | -8.5°C | 12.5°C | -28.2°C | 88% | 42 | 4.7 | 1.49 |
| February | ❄️ | -0.7°C | -4.5°C | -8.3°C | 16.5°C | -26.1°C | 86% | 38 | 4.5 | 2.09 |
| March | 🌨️ | 5.0°C | 0.4°C | -4.2°C | 26.5°C | -22.5°C | 81% | 44 | 4.3 | 3.44 |
| April | 🌨️ | 12.1°C | 6.6°C | 1.1°C | 27.8°C | -13.2°C | 76% | 57 | 4.0 | 4.66 |
| May | 🌤️ | 19.2°C | 13.2°C | 7.3°C | 33.0°C | -2.9°C | 72% | 65 | 3.3 | 5.64 |
| June | ☀️ | 24.8°C | 18.9°C | 13.0°C | 36.4°C | 2.6°C | 70% | 70 | 3.0 | 6.23 |
| July | 🌞 | 27.9°C | 22.1°C | 16.4°C | 37.2°C | 7.2°C | 67% | 69 | 2.7 | 6.21 |
| August | ☀️ | 27.1°C | 21.5°C | 15.9°C | 36.8°C | 4.7°C | 68% | 63 | 2.6 | 5.42 |
| September | ☀️ | 23.0°C | 17.5°C | 12.0°C | 34.6°C | -0.5°C | 71% | 71 | 2.9 | 4.27 |
| October | 🌤️ | 15.2°C | 10.5°C | 5.8°C | 31.3°C | -3.8°C | 77% | 63 | 3.4 | 2.76 |
| November | 🌨️ | 7.5°C | 3.8°C | 0.2°C | 22.3°C | -11.3°C | 82% | 57 | 3.9 | 1.67 |
| December | ❄️ | 1.1°C | -1.9°C | -4.9°C | 18.7°C | -22.8°C | 87% | 51 | 4.2 | 1.16 |
Showing average climate conditions across 45 years (1981–2025)
🧥 Pack heavy layers and prepare for snow — this is a Severe Winter destination.
🌤️ Early mornings and evenings are most comfortable during this Hot Summer season.
☔ Rainfall is spread across the year with no sharply defined wet season.
Monthly averages · 1981–2025 climate normals · °C
Temperatures rise steadily from spring, peak in July, and gradually decline through autumn into winter.
These seasonal patterns make summer ideal for outdoor activities, while winters bring freezing conditions and heavy snowfall.
Monthly rainfall · 1981–2025 seasonal trends · mm/month
Rainfall is concentrated in the autumn months. Humidity stays high (around 77%), peaking during winter months, which creates cold and damp conditions.
☔ Rainfall is spread across the year with no sharply defined wet season.
Monthly averages · 1981–2025
Across 45 years of records, St. Thomas's temperature shows a slight warming trend over the past decade. Its hottest day reached 37.1°C in July 1988, and its coldest dropped to -28.2°C in January 1982. 2024 was the warmest year overall and 2014 the coolest.
The warmest year in St. Thomas's recorded history was 2024 (avg: 11.2°C), while the coldest was 2014 (avg: 6.9°C).
Average annual high/low · Last 30 years · °C
Total annual precipitation · Last 30 years · mm/year
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall (mm) | Avg Humidity | Avg Wind |
|---|---|---|---|---|---|---|---|---|
2025 | 14.6°C | 9.5°C | 4.4°C | 35.9°C | -20.0°C | 392 | 71% | 3.8 m/s |
2024 🔥 | 16.1°C | 11.2°C | 6.3°C | 34.1°C | -14.7°C | 447 | 72% | 3.5 m/s |
2023 | 15.3°C | 10.3°C | 5.4°C | 33.5°C | -14.0°C | 445 | 72% | 3.5 m/s |
2022 | 14.4°C | 9.3°C | 4.2°C | 34.1°C | -20.3°C | 368 | 71% | 3.7 m/s |
2021 | 15.3°C | 10.4°C | 5.6°C | 34.4°C | -14.7°C | 402 | 72% | 3.6 m/s |
2020 | 14.7°C | 9.9°C | 5.0°C | 35.6°C | -13.7°C | 408 | 74% | 3.7 m/s |
2019 | 12.8°C | 8.2°C | 3.6°C | 31.9°C | -22.3°C | 809 | 80% | 3.7 m/s |
2018 | 13.1°C | 8.7°C | 4.2°C | 33.7°C | -22.8°C | 791 | 80% | 3.6 m/s |
2017 | 13.6°C | 9.1°C | 4.6°C | 32.1°C | -17.1°C | 851 | 79% | 3.7 m/s |
2016 | 14.7°C | 9.9°C | 5.0°C | 34.5°C | -18.6°C | 611 | 76% | 3.7 m/s |
Showing 1 to 10 of 45 years
Based on 45 years of data (1981–2025), July is typically the hottest month in St. Thomas, Ontario, with average high temperatures around 27.9°C.
January is the coldest month in St. Thomas, with average low temperatures around -8.5°C.
September receives the most rainfall with approximately 71 mm, while February is the driest with 38 mm.
The highest recorded temperature was 37.1°C in July 1988. This is part of the historical record spanning 1981–2025.
The lowest recorded temperature was -28.2°C in January 1982.
This page covers 45 years of climate data from 1981 to 2025. As new data is added to the database the page automatically reflects the updated coverage.
St. Thomas receives the most sunlight in June with an average solar radiation of 6.23 kWh/m²/day. This solar radiation data, sourced from NASA POWER, is useful for solar energy planning and agriculture in Ontario.
All climate data is sourced from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite and model data. It provides monthly averages for temperature, precipitation, humidity, wind speed, and solar radiation.
All weather data is sourced from NASA POWER (Prediction of Worldwide Energy Resources), a NASA project providing solar and meteorological data for renewable energy, building efficiency, and agricultural research.
