The strongest ice is clear or blue. Gray ice should be avoided. How thick should ice be? It's very important to remember that ice on ponds, rivers or lakes will never be 100 percent safe.

The oldest and strongest sea ice in the Arctic has begun to melt and break up, a result of prolonged warm temperatures in the region north of Greenland.

The strongest ice will be clear with a bluish tint. Weak is is formed by melted and refrozen snow and will appear milky. You should stay off ice that has slush on top.