Climate Insights for Alliston

The climate in Alliston is cool. The average annual temperature is 8°C and approximately 942mm of precipitation falls per year. Alliston receives a notable amount of rainfall throughout the year, including during its driest month. Alliston is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: July, August, June. The coldest months are February, January, December, when temperatures can drop to -10°C. Light snow can occur between January and November.

Alliston has a wide annual temperature range, spanning 36°C from the coldest to warmest months. The warmest month is July, when average highs reach 26°C and the mean temperature sits around 21°C. The coldest month is February, when overnight lows fall to -10°C and the daily average is -6°C. On average, daily temperatures fluctuate by about 9°C between overnight lows and afternoon highs. The sharpest temperature change occurs between April and May, with a 7°C shift in average temperatures.

Alliston is a moderately rainy area, receiving approximately 942mm of precipitation annually, which averages out to around 78mm per month. The wettest month is June, averaging 95mm of rainfall. April and August also tend to see above-average precipitation. The driest month is February, with just 64mm. That's 32mm less than June, the wettest month. Rainfall is relatively evenly distributed throughout the year, so there is no pronounced dry or wet season to plan around. Light snowfall can occur between January and November, totalling around 8cm annually. February is the snowiest month with approximately 3cm.

Alliston is relatively calm, with an average annual wind speed of 5km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is March, averaging 6km/h, though still comfortable for most outdoor activities. The calmest conditions occur in August, with average winds dropping to 4km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 2km/h gap between the calmest and windiest months.

It is currently spring in Alliston, which began on March 20, 2026. Alliston is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in July at around 26°C, while the coldest stretch bottoms out in February near -10°C. Summer is next, beginning on June 21, 2026 — 10 days from now.

The best time to visit Alliston is during June, July, August and September, when the weather is most comfortable for travellers. During these months, average temperatures hover around 19°C with modest rainfall averaging 85mm per month. By contrast, February can be quite cold with temperatures dropping to -10°C. Despite being the best months overall, some rain is still likely — pack a waterproof layer and plan a mix of indoor and outdoor activities.

The table below shows monthly climate averages for Alliston based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.