Temperatures are forecast to climb over the next couple of days and, as a result, Sarnia Fire Rescue is telling residents to stay off frozen waterways.
It's been bitterly cold outside over the past couple of weeks, but the mercury is expected to rise to 4 C on Wednesday and to 9 C on Thursday.
Fire Life Safety Educator Mike Otis said while it might appear to be safe, no ice is safe ice.
"There's some shelf ice forming along the lake and the bay," said Otis. "It can look solid, but it definitely isn't guaranteed to be. It's formed with waves and blowing water and ice and wind. It's cavernous underneath. So, what looks like a solid mound can be hollow underneath, and if you fall through it's virtually impossible to get yourself out. It can be a vertical drop right into the water where hypothermia and cold water shock can set in rapidly. Being the nature of the mounds themselves, someone might not be able to see that someone has fallen through. You could be down there and no one would even know you've fallen through. It's very dangerous, even for rescuers."
According to the Mayo Clinic, hypothermia occurs as your body temperature falls below 35 C (95 F).
Symptoms include shivering, slurred speech, slow breathing, a weak pulse, memory loss, and low energy.
Otis said his best advice is to admire the ice from the shoreline and never wander out onto ice mounds.
He said if you see someone fall through the ice, don't venture out to the same spot.
"It's best to throw them something that floats or reach with something like a long stick," he said. "The problem is that if you run out after them, you're just going to become a second person who needs to be rescued. We, obviously, go in with our specialized suits and ropes and everything so that we can do those rescues."
Otis said the fire department continually trains for any situations that might arise.
"Being that it's this time of the year, and ice is forming, we have been doing ice water rescue training," he said.
Otis said he can't remember the last time Sarnia Fire Rescue responded to a call for someone trapped under ice, and he's hoping it stays that way.