(ONN) – The polar vortex put a coat of ice on Lake Erie that many winter weather enthusiasts are bound to enjoy – but it comes with a warning.

The U.S. National Ice Center says a majority of the lake is covered by a 2 to 6 inch sheet – the northwestern portion closest to Detroit at 6-to-12 inches thick.

But before you go venturing out or ice fishing – warmups associated with a front this weekend can quickly dissolve that ice.

Many lakefront fire departments warn it is not as stable as it looks.

That same general rule of thumb goes for other lakes and ponds.

First responders say they too are at risk when they have to perform a rescue operation.

The Ohio Department of Natural Resources says “no ice is safe ice.”