Geoff Scoates, founder of Vancouver's Social Run Club, says the last thing he wants is for club members to suffer heat stroke.
"I'm walking around outside right now and I'm already sweating a bit," said Scoates.
He said the group cancelled its Tuesday run amid an ongoing heat wave that has sent temperature records tumbling in British Columbia.
"I think … for most of our runners, it's exhausting to think about running in this heat."
Dozens of daily temperature records have fallen in B.C. since Sunday, as a ridge of high pressure rolls from west to east across Canada. On Tuesday, 43 areas broke or tied historic heat records for July 9.
The area of Lytton set a preliminary new daily record of 42.5 C, breaking its old record of 40.6 C for July 9, which was set in 1975. Cache Creek, Lillooet and Kamloops also broke daily records with temperatures that topped 40 C.
The sole outlier was the Bella Bella area, which set a daily minimum temperature record of 6.8 C, breaking its old mark of 7.1 C for July 9 that was set in 2011.
Environment Canada said that while cooler weather was on the way by Tuesday night for some areas, including Metro Vancouver, it will remain hot in the Interior.
Health experts are warning people to be cautious while exercising in the heat and avoid going outdoors when air pollution is at its highest.
Metro Vancouver is currently under an air quality advisory for ground level smog, which will remain in place until further notice.
Dr. Michael Koehle from the University of B.C. School of Kinesiology said exercising during a heat wave risks exertional heat illnesses ranging from “severe and dangerous” heat stroke to milder heat exhaustion with symptoms including headaches, fatigue and dizziness.
“Typically, you can manage that by stopping exercise, cooling down, and having some cool fluids to drink,” said Koehle.
He said it was important to check the humidex level, which takes into account of both temperature and humidity, before exercising outdoors. Most people usually feel uncomfortable when the humidex is above 30, he said.
Koehle said that unlike smoke-related pollution, the smog now in Metro Vancouver resulted from ozone, a gas created on hot days when sunlight reacts with nitrogen dioxide and volatile organic compound.
Ozone can irritate lungs, making people cough, feel short of breath or tight in the chest, said Koehle.
He said smog can be highest on hot sunny days between noon and early evening, and air quality improves in the early morning or late evening.
A summary from Environment Canada showed 25 daily high temperature records were also set in B.C. and two were tied on Monday, from Whistler, to Trail in the southeast, Smithers in the northwest, and Campbell River on Vancouver Island.
Environment Canada said dozens of heat warnings remained in effect for much of central and southern B.C. along with the northeastern corner of the province.
The forecaster said temperatures were expected to drop to more seasonal levels by Tuesday night for Metro Vancouver, the inland sections of the north and central coasts, through Whistler and the Sunshine Coast and on Vancouver Island.
In Fort Nelson, B.C., where persistent drought fuelled the threat of early-season wildfires in the spring, the forecast showed temperatures falling from 32 C on Wednesday to 23 C on Friday and Saturday.
But it will stay hotter in the Fraser Valley, where the forecast in Abbotsford shows temperatures ranging from 27 to 29 C over the next week, while in Kamloops temperatures in the mid- to high 30s will persist over the weekend.
The Hudson's Bay store in downtown Vancouver remained closed Tuesday after keeping its doors shut during the weekend heat. A statement from the company said the well-being of customers and staff members was a top priority, and the store's heating, ventilation and air conditioning systems were undergoing maintenance.
Scoates, who has run 11 marathons in Boston, Chicago, Tokyo and Berlin, said that it was OK to exercise in warm weather, but people should be mindful of conditions.
"It can be very stressful on your body to go for a run and so in that sense, that's part of the reason we cancel," said Scoates.
Cancelling Tuesday's run in Vancouver wasn't just about the immediate risk, but was intended to send a message, he said.
"When we cancel a run like this, it sets a tone that it's OK to listen to your body and not go out when there's extreme weather," he said.
