NEVADA COUNTY A 51-year-old woman from Newcastle who went tubing with her 10-year-old son drowned when she underestimated the power of spring runoff flowing fast and cold down the Bear River.The death of Cheryl Ann Johnson on Saturday marks the third drowning in local waters so far this spring and is a dark reminder for swimmers and recreationists to use caution when flocking to area rivers when temperatures heat up.The river is up quite a bit. I cant believe they went down there pretty dangerous, said Capt. Art Schreiber of the Peardale-Chicago Park Fire Protection District, who first got the call of a possible drowning at 4:14 p.m. Saturday.People seeking relief from the heat along area streams, rivers and lakes are reminded that water temperatures will continue to be very cold and to be aware of the dangers of hypothermia, warned the National Weather Service in a special weather statement over the weekend.Wear a life jacket if you will be in the water and be sure children are wearing a life jacket if they are even near the water, the statement read.Johnson and her son launched their inner tubes into the water at the Bear River bridge on the Nevada County side of the river, a few miles from the town of Colfax, Schreiber said. The boys father was to meet them a short distance down river at the Bear River Campground.Johnson, who had reportedly never been tubing before, was caught off guard by the fast water.The water was moving so fast by the time she hit the first currents, she knew she was committed, Schreiber said.Johnson was thrown from the tube and trapped in a rock formation under water where she drowned, according to the Placer County Sheriffs Department.Johnsons life preserver did not save her.Hers was not secured properly, Schreiber said.The boy was swept down river and kept afloat by his life jacket until he reached the bank, unable to rescue his mother, according to officials.A man who was gold panning at the rivers edge heard the boys cries for help and ran back to Highway 174 to find someone to call 911. A group of four young adults tried to help Johnson escape the place in the rocks and rapids where she was pinned, but it was too dangerous, Schreiber said.Its not only high, its swift, Schreiber said.Eight fire and rescue teams from Placer and Nevada County responded. Some rescuers hiked 112 miles along a dirt trail to the place where the woman was caught in the current, Schreiber said.A dive team from Placer County performed a swift water rescue to recover Johnsons body. She was carried back to the bridge at about 10:30 p.m., Schreiber said.The boy was flown by helicopter to the Peardale-Chicago Park Fire Protection District where he was given medical attention then released to his father. The boy is in good condition, according to Sgt. Brian Whigam of Placer County Sheriffs Department.Last month, Daniel Farris, 22, of Yuba City, died when he dove off a rock into a pool below Beale Falls located in Spenceville Wildlife Area.Mollie Taplin, 31, of Nevada City was found the same day, floating face down in the South Yuba River near Edwards Crossing.A heat wave with unseasonably hot May temperatures in the valley and foothills peaked Sunday and spring-like temperatures are forecast to return by mid-week into the upcoming holiday weekend.Over the weekend, temperatures hit 106 degrees in the Central Valley, a high considered 20 to 25 degrees above normal, according to the National Weather Service.Sacramento typically doesnt reach its first day of 100-degree heat until June 19.