From toasty to frosty, spring frost by the numbers for the Maritimes

Clear sky, light wind and temperatures falling towards zero. That’s the recipe for frost and what is in the forecast for parts of the Maritimes Thursday night.

The May heat has broken. It peaked on Wednesday when all three Maritime provinces set new daily high temperature records for a May 20.

On Thursday, a much cooler brand of air flowing in from off Hudson Bay is in place for the region. The cool down brings daytime high temperatures on Thursday back down into a more seasonable range of the low-to-mid teens.

A clear sky and a light wind will help low temperatures Thursday night into Friday morning fall towards the low single digits and in some cases near freezing. That will bring the Maritimes a risk of frost.

The highest risk of frost for Thursday night is in northern and central New Brunswick. There is a lower risk, but a risk none the less, of patchy frost in southern New Brunswick and Nova Scotia. I would also include a low risk of frost in interior areas of Prince Edward Island. Frost advisories have been issued for parts of the Maritimes.

Plants at higher risk of being damaged by frost include some vegetables like tomatoes, peppers and cucumbers. Herbs such as basil and annuals like marigolds and petunias are also at risk.

A similar risk of frost in the Maritimes looks likely for Friday night into Saturday morning.

It isn’t unusual for the Maritimes to have a risk of frost for this time of the year.

Looking at some average dates of last frost for the region shows that much of the Maritimes experiences a final frost late-May through early June. Keep in mind that is an average. That means that some years a frost has occurred past that general time.

If gardeners really want to play it safe, we can look at statistics for dates in the region when there is a 10 per cent chance of frost on-or-after. For that, most of the coastal communities of the Maritimes are out of a risk of frost by late May and most of the interior areas are out by mid-to-late June. One area, the higher terrain in northwestern New Brunswick, has reported some rare frost in early July.

I’m sure many have heard the general rule of waiting for the June full moon before assuming the risk of frost has passed. Given the frost statistics, that usually works out for the Maritime provinces. The June full moon isn’t until June 29 this year, at the very end of that month.