No way to predict if frost is coming more than two days out, climatologist says
Nelson Zandbergen
Farmers Forum
CHATHAM-KENT — Southwestern Ontario saw overnight freezing temperatures on at least two nights in late May. Major grain and oilseed commodity crops were mostly unscathed by Jack Frost, but some tender fruits and tomato plants were not.
Temperatures dipped below 0 C on May 17-18 and May 24-25 in large swaths of the region. But wet conditions in April and early May kept many farmers off the fields and the newly planted grain seed (especially corn) hadn’t emerged to incur damage.
Environment Canada Senior Climatologist David Phillips said a “significant” killing frost of -1.4 C hit the London area early on the morning of May 18. “A lot of frost hollows, a lot of low-lying areas will get nipped by that,” Phillips observed, noting that London is a good barometer for southwestern Ontario generally.
He could recall only one later frost to hit the London region in the last 20 years, a low of -1.3 C on May 23, 2015. Otherwise, records show no frost later than April 30.
The old rule of thumb was that frost could hit southwestern Ontario after May 23 about 10 % of the time, he said, although this has declined in the last 30 years.
Phillips explained that spring is a time when arctic air and tropical air jockey for position over Ontario and you can never rule out an incursion of arctic air. Combined with clear overnight conditions and lack of wind, temperatures can drop below freezing.
Phillips also suggested the best forecasts and observations give farmers no more than a couple days notice. Weather experienced in March or April doesn’t predict, or correlate with, the likelihood of frost weeks later in May, either, according to Phillips, who noted that April briefly hit a high temperature near 30 C this year.
Elmwood-area beef producer and cash-cropper Ken Schaus reported three nights of frost at his operation during the week of May 18. The corn crop was “just starting to pop through” and wasn’t damaged. “I would say it slowed the pasture growth and for sure slowed some of the hay growth.”
Schaus said he reduces the odds of frost damage by not planting earlier than May 5. In the last couple of years, he said, corn planted by May 1st has been out-yielded by corn planted on May 12-13 anyway. He would rather avoid replanting a crop because it was planted too early. “You can roll the dice if you want, but seed’s not cheap and diesel fuel’s not cheap. I’d rather have one nice pass and have it done.”
Woodstock-area cash-cropper Kevin Armstrong said the crops in his area were not affected by the cold temperatures. He said he has no way of knowing in April if the spring will serve up untimely frosts in the weeks ahead — not even a gut feeling. “I’ve never not planted because I thought there was going to be a weird come-out-of-the-dark frost,” he said. Frost damage early in a corn plant’s life, he added, “doesn’t really affect yield. It might set the plant back, but usually it does grow out of it.”
He’s willing to plant early, say April 18th or 19th, he said, so long as the ground is fit. In his neighbourhood, growers “want to get it in the ground when the ground is ready … to get the yields that will pay for those inputs,” he explained.
The Armstrong operation previously adjusted to seasonal challenges by moving to lower heat-unit corn, which matures and dries down earlier. “But that’s more of a fall issue,” said Armstrong, who’s since gone back to growing longer-season corn this year.
Field tomatoes, which are transplanted as seedlings, were more susceptible. Adam Dick, chief operating officer at Chatham-based Tomato Solutions — a tomato seed producer — reported that a large client lost 600 acres of tomato plants in the frost. “They were going to order more seed, but they ended up reducing their plant population.”
Dick said the industry was lulled by warmer temperatures earlier in May, leading some growers to start planting on May 10, two weeks ahead of the standard Farmer’s Almanac May 24 rule that still loosely applies to tomatoes. “That ended up being a mistake. We basically broke our own rule. People are inclined to believe in climate change a little bit, but that turned out not to be the case, at least not locally here. Not this time.”
He said there was no good way of divining in advance if the planting season will face an untimely frost. “It’s really tough. You almost need a hotline to the gods,” he quipped. “There are trend lines and because it was warm, people thought it was going to stay warm, but no, it (the climate) is an unpredictable, nonlinear system.”
Blueberry bushes are coated with ice at Parks Blueberries, in Chatham-Kent. Co-owner Hope Parks says that sprinklers spraying water prevent the blueberry tissue from freezing as long as liquid water flows over the ice-covered blueberries.
Meanwhile, sprinklers protected the delicate blueberry bush blossoms when frost touched down at Parks Blueberries, also in Chatham-Kent. Co-owner Hope Parks said they won’t know for sure until the berries are harvested later this summer but it appears the 40-acre plantation came through without damage. The operation drew some attention on social media with images of blueberry bushes encoated with ice as the sprinklers ran, a process that prevents the tissues from freezing so long as liquid water flows over the ice.
Apple blossoms were also out at the time of the freeze but damage doesn’t seem to be extensive in the orchards of the southwest. “I would say some individual farmers will have suffered crop loss but we may not see much of a difference in the Ontario crop overall,” Cathy McKay, Ontario Apple Growers chair, told Farmers Forum.
McKay said she sustained some damage at her own Whitby-area orchard, where the mercury dipped to -2 C. At temperature drop to – 2.2 C equates to a 10 % yield loss, while -4 C will wipe out 90 % of an apple crop, she said.
London-area orchard operator Philip Crunican reported no damage. He deployed two trailer-mounted “frost fans” to help move the air and prevent frost on 30 acres of apple trees, although the units may not have been needed because of the natural breeze. He explained that it’s on cold, still nights that the diesel-powered, 30-foot tall fans work to mix colder air at ground level with slightly warmer air above to prevent freezing. The process only works effectively down to about -5 C.
