First Frost


Everywhere I look the first frost is being forecast by yearly averages. Depending on the source I am getting dates from as early Oct. 10 to as late as the second week of november.
Would anyone have a better idea on when we will be getting first frostthis year in east york?



I have found the wide variation in reported first and last frost dates confusing and frustrating too. In a search just now, I found the last spring frost date reported for Toronto to be between May 4 and April 30 and the first fall frost date to be between October 13 and November 10. I think the first frost date for fall 2018, in my backyard in downtown Toronto, was in early November.

Frost dates are the days of the year when it is calculated to be 50% likely that that the temperature will go below freezing resulting in frost on the ground. The Farmer’s Almanac used data from 1981 – 2010 for it’s dates. Their dates don’t take into account that we have had 3 of the warmest years ever in the last 5 years.Frost free dates are simply estimates and cannot account for unusual weather events, microclimates (which can be caused by many factors, including large areas of concrete and steep changes in elevation) and the fact that plants react to a variety of factors other than temperature, such as light, humidity, soil type and the duration of cold temperatures. OMAFRA gave a bit more specific information in relation to vegetable crops: The published frost dates refer to the occurrences of 0 deg. C at a standard height of 1.5 m and which time tender crops will often be damaged. Frost-hardier crops are not usually damaged until temperatures at this height drop below -2 deg C. The date of occurrence of -2 deg C is usually about 2 weeks earlier in the spring or later in the fall than the published frost free dates.

All of this is to say that there is no absolutely accurate information for weather that is yet to come. As you pointed out, published dates are estimates. I would say that from now on, if you have treasured plants or vegetables that you want to cover, you should be checking the weather every few days and taking action based on these reports. I use the Weather Network, but many of my gardening friends prefer Environment Canada. Google Environment Canada Toronto weather forecast. They probably have a smart phone app. I did hear a CBC meteorologist say recently that it was going to get cold earlier in Toronto in 2019 than in 2018. Weather forecasts are quite accurate for up to 3 days in the future, so I think checking frequently is the only way to be safe.