Ontario, Canada's most populous province, spans a vast area from the Great Lakes in the south to Hudson Bay in the north. Its climate varies significantly by region, but the most populated area—Southern Ontario, including the Greater Toronto Area (GTA)—experiences a humid continental climate with four distinct seasons. This article provides a month-by-month overview of typical weather conditions in Southern Ontario, focusing on temperature, rainfall, and daylight hours. Data is based on historical averages from Environment and Climate Change Canada for Toronto Pearson International Airport (1981–2010 normals).
January — Deep Winter
January is the coldest month in Ontario. Average high temperatures hover around -1°C (30°F) and lows drop to -10°C (14°F). Snowfall is common, with an average of 30 cm (12 in) accumulating in Toronto. Daylight hours are short: sunrise around 7:45 AM, sunset near 5:00 PM, giving about 9 hours of daylight. Precipitation averages 60 mm (2.4 in), mostly as snow. Lake-effect snow can increase totals east of Lake Ontario.
February — Still Cold
February remains cold, with average highs of 0°C (32°F) and lows of -8°C (18°F). Snowfall continues, averaging 25 cm (10 in). Daylight increases to about 10.5 hours by month's end. Precipitation is similar to January at 55 mm (2.2 in). Occasional thaws can bring rain, but winter conditions persist.
March — Transition to Spring
March sees a gradual warming. Average highs reach 5°C (41°F), lows around -3°C (27°F). Snowfall declines to 15 cm (6 in), but rain becomes more frequent. Total precipitation is 60 mm (2.4 in). Daylight jumps to over 12 hours by the equinox (March 20). The first signs of spring appear, but frost is still common at night.
April — Spring Showers
April is a wet month with average rainfall of 70 mm (2.8 in). Snow is rare. Highs average 12°C (54°F), lows 3°C (37°F). Daylight extends to 13.5 hours. The risk of frost diminishes by month's end. Gardeners begin planting cool-season crops. Toronto's climate overview notes that April is one of the cloudier months.
May — Pleasant Spring
May brings comfortable weather. Highs average 19°C (66°F), lows 9°C (48°F). Rainfall is moderate at 65 mm (2.6 in). Daylight reaches 14.5 hours by late May. The last frost typically occurs in early May. Trees and flowers bloom fully. This is a popular time for outdoor activities.
June — Start of Summer
June is warm with average highs of 24°C (75°F) and lows of 14°C (57°F). Rainfall is about 70 mm (2.8 in), often from thunderstorms. Daylight peaks at 15.5 hours around the solstice (June 21). Humidity begins to rise. Lake Ontario water temperatures reach 15°C (59°F), suitable for swimming only for the hardy.
July — Hottest Month
July is the hottest month. Highs average 27°C (81°F), lows 17°C (63°F). Humidity can make it feel like 35°C (95°F). Rainfall averages 75 mm (3.0 in), often from brief downpours. Daylight is about 15 hours. Heat waves can push temperatures above 30°C (86°F). Air conditioning is essential. The best time to visit Toronto is often considered late spring or early fall to avoid the summer heat and crowds.
August — Warm and Humid
August continues warm with highs of 26°C (79°F) and lows of 16°C (61°F). Humidity remains high. Rainfall is similar to July at 75 mm (3.0 in). Daylight decreases to 13.5 hours by month's end. Lake water temperatures peak at 20°C (68°F). Thunderstorms are common.
September — Early Autumn
September brings milder weather. Highs average 22°C (72°F), lows 11°C (52°F). Rainfall is 70 mm (2.8 in). Daylight falls to 12 hours by the equinox (September 22). Humidity drops. The first frost can occur late in the month in rural areas. Fall foliage begins in late September.
October — Crisp Autumn
October is cool. Highs average 14°C (57°F), lows 5°C (41°F). Rainfall is 65 mm (2.6 in). Daylight shortens to 10.5 hours. Peak fall colors usually occur mid-month. Frost becomes frequent. What to pack for Toronto in October includes layers and a warm jacket.
November — Late Autumn
November sees a significant drop. Highs average 8°C (46°F), lows 1°C (34°F). Precipitation averages 70 mm (2.8 in), often as rain but occasional snow. Daylight falls to 9 hours. The first significant snowfall usually occurs in late November. Overcast skies are common.
December — Winter Returns
December is cold. Highs average 2°C (36°F), lows -5°C (23°F). Snowfall averages 20 cm (8 in). Total precipitation is 65 mm (2.6 in). Daylight is minimal: sunrise around 7:45 AM, sunset at 4:40 PM, giving just over 8 hours. The winter solstice (December 21) has the shortest day.
Regional Variations
Northern Ontario (e.g., Thunder Bay, Sudbury) is colder with more snow. Average January highs are -10°C (14°F) and lows -22°C (-8°F). Snowfall can exceed 100 cm (39 in) annually. Daylight in winter is slightly shorter. Southern Ontario's Niagara region has milder winters due to lake effects from Lake Erie. The Ottawa Valley experiences colder winters and warmer summers than Toronto.
Practical Tips
- Winter (December–February): Pack a heavy winter coat, boots, hat, and gloves. This packing guide has details.
- Spring (March–May): Bring a waterproof jacket and layers. Rain is frequent.
- Summer (June–August): Light clothing, sunscreen, and an umbrella for thunderstorms. Consider visiting in late spring or early fall for milder weather.
- Fall (September–November): Layers are key. A medium-weight jacket suffices until November.
For a broader context, see the Toronto climate overview.