SALT LAKE CITY -- A spike in temperatures means Utah's mountain-fed rivers and streams are quickly swelling -- some tripling in volume in a matter of days -- and raising the risk for those who go near them.
Winter accumulations of snow began melting rapidly Monday, said National Weather Service hydrologist Brian McInerney.
However, he said, the runoff may briefly slow again, with a cooler spell expected later this week.
He's warning parents to keep youngsters away from fast-moving streams. Each year, he said, children fall into and drown in Utah's frigid, mountain rivers.
"It's frighteningly cold water," McInerney said.
Unified Police Lt. Don Hutson said his agency, a Salt Lake County police force, trains vigorously for swift-water rescues that can be common this time of year.
The danger is not just that the water is moving fast through rocky areas but also that river temperatures can be in the mid-30s, and hypothermia can set in within minutes, Hutson said.
Dangerous conditions are expected to remain until early June.
Flows for rivers fed by mid- and high-mountain melts are forecast to peak around May 27.
In some areas, 1 to 2 inches of mountain snow is expected to melt per day.
The Weber River near Oakley -- like similar rivers in the Wasatch range -- is expected to triple its water between now and the end of the month, McInerney said.
Despite that, flooding isn't expected this spring.
That's partly because Northern Utah got less snow than average over the winter. Storm systems in March and April helped, McInerney said, but the northern mountains are still lagging behind the 30-year average.
In Southern Utah, where snow was more plentiful, McInerney said pre-existing channels will help keep rivers within their banks.
Temperatures were expected to reach 83 in Salt Lake City on Monday before cooling for the remainder of the week.