A wet, hot Yukon summer

Whitehorse residents will have noticed that it rained a lot over the past few months. In fact, both rainfall and temperatures have been well above average this summer.

Whitehorse residents will have noticed that it rained a lot over the past few months.

In fact, both rainfall and temperatures have been well above average this summer.

Environment Canada statistics show the city received 30 millimetres of rain in April, 44 in May and 47 in June.

The normal levels for those months are seven, 16 and 32 millimetres, respectively.

Only July so far has been comparatively dry, with 19 millimetres instead of 38.

But it’s the temperatures that broke the most records.

“We did end up with a very warm spring,” Environment Canada meteorologist Lisa Coldwells told the News.

“That’s why it seemed the summer was longer.”

For March, April and May, the average temperatures were 3.9 C higher than the previous record, set in 2015.

Last March 31, it hit 16.8 C in Whitehorse.

The highest temperature recorded for any March 31 in the past 70 years is 2.9 C, and for March in general, 11.7 C.

The warm spring can be directly linked to El Nino, a meteorological phenomenon caused by warmer water in the Pacific Ocean around the equator, Coldwells said.

Interactions between the ocean and the atmosphere result in warmer ocean water near North America’s Pacific coast and warmer temperatures.

Because it takes five to six months for its effects to be felt in the Yukon, the result here was a warmer winter and spring.

El Nino is a cyclical phenomenon, which is now ending, Coldwells said.

But American scientists monitoring the Pacific Ocean are now predicting the inverse phenomenon, La Nina – colder ocean water resulting in colder weather.

If it turns out to be accurate, next year’s spring and late winter could be colder.

For now, Coldwells cautions those are projections with a 60- to 70-per cent probability.

“It’s difficult to say what it’s going to be,” she said. “We’re really pushing off in the future.”

Then there’s the impact of climate change.

“El Ninos have always been going on,” Coldwells said.

“What we’ve seen is they have increased in their frequencies.”

In the meantime the winters have steadily gotten warmer in the past 15 years.

“Back in the 1990s it was very common to see deep freeze temperatures,” she said.

“They were more prolonged cold spells that we’ve seen in past.”

For Coldwells, who has been forecasting for the Yukon and the Arctic since the 1980s, what’s not unusual is the large amount of thunderstorms that took place over southern Yukon in the past six weeks.

“Having thunderstorms roll through is not a weird occurrence,” she said.

The Yukon has a so-called continental type of weather, similar to Alberta, with the mountains creating conditions favourable for thunderstorms.

The sun heats up pockets of air on mountainous terrain. With enough instability, those turn into thunderstorms and rainstorms. And because of the many mountains, they can be highly localized.

The heavy rainstorm that happened on the evening of July 12 only flooded part of the city.

Environment Canada’s rain gauge at the Whitehorse airport only recorded five millimetres of rain, yet sections of Riverdale were so heavily flooded that cars had difficulty passing through the water.

Looking at videos of the flooding, Coldwells estimates about 15 millimetres of rain came down in 10 minutes in parts of Riverdale and downtown.

“It’s very localized — that’s the type of precipitation in the summer.”

“It’s hit or miss, not a huge rain storm that’s going to affect entire south Yukon.”

In comparison, a Vancouver winter rainstorm is completely different, she said. “Everybody gets rain.”

The heavy rainfalls have a direct impact beyond less time spent watering veggies in the backyard: lower numbers of wildfires.

Heavy lightning, which accounts for a significant chunk of wildfires in the territory, only started a few fires this year, said Wildland Fire Management spokesperson George Maratos.

“When you look at the fire numbers, it’s understandable our numbers are down,” he said.

Despite great advances in weather forecasting, it’s anybody’s guess how long the summer weather will last.

Coldwells wouldn’t speculate about that, since forecasts have at most a 10-day range.

So enjoy those patches of blue sky while they last — soon enough we’ll all have to retreat inside.

Contact Pierre Chauvin at

pierre.chauvin@yukon-news.com

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