TROUTDALE, Ore. – Lifeguards began manning area swimming hotspots over Memorial Day weekend to head off any trouble after a drowning already claimed two lives in the area this month.

The quick snowmelt has flooded area rivers with fast-running, very cold water.

American Medical Response said it was the eleventh season of its River Rescue Program. Teams were set to stake out Glenn Otto Community Park along the Sandy River in Troutdale, and High Rocks Park along the Clackamas River in Gladstone.

Kirk Dunn, 22, drowned after he and a group of friends went swimming on the Sandy River last Sunday. That led to Troutdale Mayor Jim Kight to ask beach-goers and fishermen not to swim in the rushing waters. Later in the week, 27-year-old Dustin Fergusen is believed to have drowned in the Wind River in Southwest Washington.

Rescue crews say the rivers are deceptive, looking somewhat calm on the surface, but cold and rushing waters underneath also hide dangers like fallen trees and rocks.

"That creates difficult challenges for people coming down to swim, see placid water, want to get in it, and then hit a strong current very quickly," AMR lifeguard Taneka Means said.

Water temperatures were also hovering not far above 40 degrees.

"You get stiff, it becomes hard to swim," swimmer Terri Schmidt said. "It's kind of unexpected. It's a shock to your system."

Lifeguards will staff the two popular swimming through the summer until Labor Day.

(KGW Reporter MIKE BENNER contributed to this report)