VANCOUVER -- A person's tragic death while they were swimming in a Lower Mainland river has prompted a warning from local search and rescue teams as temperatures are expected to soar in the region.

Coquitlam Search and Rescue shared the story on social media Wednesday, saying a person was "swept away in fast moving water while swimming at Widgeon Falls," near Pitt Lake.

Crews say it took hours to search for the subject, but their body was eventually recovered.

"Our sincerest condolences to the family and friends of the deceased," Coquitlam Search and Rescue's post says.

"This is a sobering reminder to always use caution around fast moving water. Rising temperatures can increase snowmelt from the mountains above which can cause water levels to fluctuate throughout the day."

The team's cautioning comes as nearly all of B.C. is under a heat warning. Environment Canada says an "exceptionally strong" ridge of high pressure could leave parts of the province dangerously hot from Friday until Tuesday. 

"The duration of this heat wave is concerning as there is little relief at night with elevated overnight temperatures," the warning, which was issued Wednesday afternoon, says.

"This record-breaking heat event will increase the potential for heat-related illnesses."

Warnings have been issued in most regions of the province, including Metro Vancouver and the Fraser Valley.

Environment Canada said temperatures could reach as high as 38 degrees during the day in Coquitlam, Maple Ridge, Surrey, Langley, Abbotsford, Chilliwack and Hope – and stay as high as 20 degrees overnight.

With files from CTV News Vancouver's Andrew Weichel