British Columbia

Why B.C. may be in for a long, hot summer

CBC meterologist Johanna Wagstaffe takes an in-depth look at the unusual factors driving the coming heat wave and what it means for summer time on the West Coast.

A dry spring, a warmer than usual Pacific Ocean, and an El Niño means the hot weather could be here to stay

The core of B.C.'s heat is coming from an air mass moving northward from the southwestern U.S. (Johanna Wagstaffe/CBC)

Whenever temperatures approach 30 C in Metro Vancouver, it's a talker.

While the thermostat does get close once or twice each summer, this particular heat wave has a lot of added factors. First of all, it's early, as seasonal highs for Vancouver right now are just 20 C.

And the forecast temperatures will likely end up 10 degrees above that this weekend — numbers more reminiscent of July or August.

This heat wave will also be intense. Temperatures will steadily climb right across southern B.C. over the next few days, peaking on Sunday at 30 degrees for the South Coast and approaching the 40s in the Interior.

Daily temperature records will fall, but so too will many all-time hottest June day records. It looks like we will, at least, get close for places like Vancouver (30.6 C), Kelowna (38 C) and Kamloops (39.1 C).

Finally, this heat is just the latest 'extreme' in what has been an incredibly warm and dry year overall. Most of B.C. is coming out of a winter of record low snow packs.

Long range forecast calls for hot summer

This past May was the driest on record for most of the province. So far, just a fraction of expected June rain has fallen. And in general, temperatures have been above seasonal for weeks on end.

This provides that much more of an impact for the hot weather forecast when it comes to fire danger and drought concerns. After an explosive start to the fire season, and reservoirs dropping at an alarming speed, a dry forecast ramps up the danger and a hot one means evaporation of any moisture happens at a faster rate.

Now for the 'why': the weather story for months has been a persistent high pressure system sitting off the B.C. coast. It has not only kept us protected from Pacific rain-makers, but it's also ushered in warmer temperatures.

The driving factor here is warmer than normal sea surface temperatures over the eastern Pacific, are here to stay for the summer thanks to a strengthening El Niño.

This weekend, a slightly different set up is occurring. The core of our heat is actually coming from the southwestern U.S. It's being driven north by a strong high pressure system sitting over Arizona that is directing hot, dry air that forms over the desert and makes its way up into the Pacific Northwest. 

Small chance of a break

So when will B.C. catch a break? It's generally a hot and dry forecast through the weekend and through next week. But there are a few mini breaks to watch out for.

Afternoon thunderstorms are possible right across B.C., including for Vancouver on both Saturday and Sunday. They will be isolated if they happen, and will also bring the risk for fire-starting lightning. There may also be some quick rain Monday night into Tuesday before the forecast dries up again. And it will.

Long range outlooks for the West Coast continue to show a strong likelihood the heat will continue. Your best bet this weekend may be the beach. Temperatures will be a good three to four degrees cooler than even a few blocks inland.


Johanna Wagstaffe

Senior Meteorologist

Johanna Wagstaffe is a senior meteorologist for CBC, covering weather and science stories, with a background in seismology and earth science. Her weekly segment, Science Smart, answers viewers' science-related questions.


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