Judging ice conditions on many lakes and reservoirs can be a tricky call for even an experienced outdoor recreationist.
"Anglers, snowmobilers, ice skaters and others should use extreme caution whenever venturing onto the ice," said Liz Lodman, coordinator of Montana Fish, Wildlife & Parks' vehicle safety program.
Sunny days and warm winds are not the only conditions affecting ice thickness and strength, Lodman said. Springs and rising or moving water erode ice on its underside. This erosion is often invisible and uneven -- some areas are weakened, while others are not. Ice covered by a layer of slush or water, and ice with dark-colored spots, are signs of thin ice that should be avoided.
"Never assume ice is safe by just looking at it," warned Lodman. "Use an auger or spud bar to test the thickness and condition of ice. Since ice usually melts faster along shorelines, anglers should leave their vehicles on the shore."
Recreationists should keep in mind that ice that appears safe in the morning can quickly thin or melt by afternoon, leaving them in a dangerous situation or even stranded, Lodman said.