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Frost fades and it’s finally safe to start gardening in southern Ontario

Friday, May 14th 2021, 12:01 pm - Despite a sputtering spring, this could be the year to get into the garden sooner than you think.

A common rule of thumb for gardeners is to wait until after the May long weekend to plant outdoors in order to avoid the threat of frost. This spring in particular across southern Ontario has also shown its temperamental side. After starting out strong, it seemed to sputter, with persistent periods of well below seasonal temperatures and early widespread frost advisories across the region.

MUST SEE: Sudden summer for parts of Canada – does it last for the long weekend?

Now, as we head towards the May long weekend -- the unofficial start to summer -- many gardeners are anxious to start planting.

Based on a recent poll question we put out, an overwhelming 65 percent of those who answered said the May 24 weekend is definitely the marker for their outdoor planting, while about 25 percent said they like to wait until June.

Jason Boyce said his grandmother's advice for June planting has never steered him wrong.

"My grandmother, who won awards for her gardening, always said, “The 4th of June by the light of the moon.” It’s always worked for me too!," Boyce tweeted.

This could be the year however, to get into the garden sooner than you think. It all depends on location - and the fact that the long weekend is later in the month this year.

NatPattern MAY3RDWK 21

British Columbia is always lucky to see the first signs of spring every year, thanks to their relatively milder winters and Pacific flow. The Prairies on the other hand have already had a taste of warm weather, and in the coming days will likely be the first region to race to 30-degree highs. But long-range models are also hinting at the threat of a cool down and even the threat of snow. Parts of Atlantic Canada might want to be cautious, as temperatures may still be a touch on the cool side in the coming days and weeks, despite the current pattern change underway.

For gardeners in Ontario and Quebec, some good news as the threat of frost seems to have passed for most areas. That's after some frosty nights earlier in the week that may have left some desperate to protect their delicate plants.


Temperatures across southern Ontario are finally trending upwards, with seasonal daytime highs around 20°C expected into next week. But more importantly, overnight lows aren’t expected to be frosty.

The graphic below, put out by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), shows the average date for the last spring frost.


Southwestern Ontario, Niagara and areas along the 401 corridor typically see the last frost between mid-April and early May. The farther inland and northward you go, last frosts can be around the end of May.

Northern Ontario will typically see the last frost around the first to second week of June.


According to the OMAFRA, 50 percent of the time (one year in two), there will be no frost in these locations after that date.

"There is a 25 percent risk of a frost occurring seven days after the listed last spring frost date. Fourteen days after the listed date, the risk decreases to 10 percent," the OMAFRA says.

Let's get growing, gardeners!

Thumbnail image courtesy: Pixabay

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