Last week’s cold snap came at a critical time for the Okanagan’s cherry crop. Record-tying low temperatures of -7.8 Celsius in Kelowna had some cherry orchardists calling in helicopters to help stir up the air and raise temperatures in the orchard above critical levels on Wednesday night, April 2.
Hank Markgraf is a Kelowna orchardist and a board member of the International Tree Fruit Association. He says on Wednesday night and around a week ago, cool night-time temperatures had growers turning on their wind machines and in some cases where those weren’t available, calling in helicopters to coax a warmer inversion layer above the orchard closer to the ground.
"We’re at a critical time in the cherry crop. Anytime buds start growing, we have to keep temperatures above what are known as critical temperatures,” Markgraf says. “Some Kelowna orchards used helicopters to try and coax that layer down,” he says adding helicopters aren’t normally used for this purpose in B.C. It’s done more often in Washington State and New Zealand. We normally use helicopters as a drying technique in June or early July.”
According to infotel.ca, the critical temperature for cherries in Kelowna this week was around -5 to -6oCelsius. Markgraf says for the helicopter to work effectively, there has to be an inversion layer to stir up, and second, that layer needs to be at an elevation where it can mix with the cooler ground air.