Hotter nights cause problems for crops

The historic, unprecedented, scorching, roasting and record-setting temperatures across Western Canada in late June and early July have been bad news for canola crops on the Prairies.

Canola prefers cool weather during the crop’s flowering stage because prolonged temperatures above 30 C usually cause heat blast, which shortens the bloom period and reduces yield.

Temperatures in the high 30s to mid 40s in the last week of June and into early July are alarming, but this was not the first heat wave in the history of Western Canada. Environment Canada historical weather data shows that heat waves were a common occurrence in the past.

The daily highs rarely reach 37 C or 39 C in places like Brandon, Lloydminster, Regina and Red Deer, but July days with temperatures above 30 C were actually more commonplace in Western Canada in the 1970s and 1980s.

The Western Producer looked at Environment Canada weather data in two locations — Brandon and North Battleford, Sask.

• From 2013-20, there were 19 days in July when the daily high exceeded 30 C. On average, that’s less than three days per July.
• From 1983-90, there were 70 days in July when the daily high topped 30 C. That’s about nine days per July, on average. In 1989, alone, there were 17 days when temperatures exceeded 30 C.
• From 1973-80, 54 days in July exceeded 30 C, or more than six days per July.
• From 2013-20, there were 12 days in July when temperatures topped 30 C.
• From 1983-90, there were 21 days above 30 C.
• From 1973-80, there were 24 days above 30 C.

If 2012 is included in the Brandon data, the number of July days in the last decade with temperatures above 30 does increase because July of that year was a scorcher.

However, daily high temperatures in the summer aren’t getting much hotter on the Prairies or across Canada.

“What you’re seeing (in the data) doesn’t surprise me,” said Barrie Bonsal, a research scientist with Environment and Climate Change Canada in Saskatoon.

“For example, in the prairie drought decades of the 1930s and 1980s, we had quite a bit (more hot days in the summer) than we did in the last 10 years.”

The data may show that the Prairies had hot summers in the past, but it’s difficult to remember a scorching week in July that happened 35, 45 or 85 years ago.

Humans and the news media focus on the here and now. When the temperature hits 37 C for several days somewhere in Canada, it generates widespread media reports about how climate change has arrived.

“Unfortunately we are living it already — it’s not the future, it’s here… so I hope people take the time to get better prepared as we will likely be seeing this more often,” Natalie Hasell, a meteorologist with Environment Canada, told CTV News.

It is correct to say that the climate is changing and the average temperature in Canada is getting warmer. But the historical data tells a clear story — it’s getting warmer at night and less cold in the winter.

“The night time temperatures are increasing more than the daytime temperatures … and the winter temperatures (are increasing) more than the summer temperatures,” Bonsal said.

“(We’re) pretty confident that is going to continue.”

That trend is problematic for canola growers because the crop does better when temperatures cool off at night, which allows the plants to rebound from a warm day.

“Cool nights offer some recovery…. Warm nights do not provide a recovery period, and more flowers are aborted, producing blanks along the stem,” the Canola Council of Canada says on its website.

As for the recent heat dome that pushed temperatures into the 40s in parts of Western Canada, similar events have happened in the past on the Prairies. Climate data shows that a week of 32-35 C weather in July occurred multiple times in the 1930s, 1970s and 1980s.

But looking ahead, it’s possible that heat domes will produce summertime temperatures that are more extreme, Bonsal said.

“With a warming atmosphere, when we get these heat domes, they might last longer or they’ll be more intense. Or they’ll be earlier in the (summer)…. They could also occur more frequently. That’s where the climate change aspect comes in.”