Ice covering rivers and reservoirs around Calgary should never be considered safe to walk on, fire officials say. ((Meghan Grant/CBC))

Fire officials are reminding Calgarians that ice on the rivers and reservoirs around the city can be very dangerous.

Because of the freeze-and-thaw cycle brought on by Calgary's frequent chinooks, ice on the Bow and Elbow rivers and the Glenmore Reservoir is not safe to walk on, said fire department spokesman Brian McAsey.

"We had a mother, her two children, walk out on this ice.… She didn't realize that there was a great danger.… Very scary situation," he said.

McAsey added that it is illegal to venture onto the ice at the reservoir.

And while there is no law against walking on the river ice, McAsey said people should assume that all ice is dangerous.

"That ice is not of a quality thickness. And so it is undependable, and once someone's on the ice it's very likely they'll fall through it," he said.

"And if a person is submerged in that water, they can then become trapped underneath the ice."