Different combinations of environmental and load factors do not allow for a sure-fire standard to be developed. The only way to eliminate the risk of accidentally breaking through the ice, is to close open-water venues to the public. However, in the interest of tradition and winter-time recreation, the risk can be reduced through conservative approaches. Some agencies have already done this by establishing thickness benchmarks. A small study by the Bartlett Park District in 1991 indicated that ice thicknesses of four to ten inches were being used as benchmark measurements by survey respondents.
Snow ice is only about half as strong and melts quicker.
During warm periods, ice can melt from both the top and from the bottom. In fact, the water temperature below the surface can be warmer. Water flooding up through the hole is a dangerous sign. Ice can be weakened by salt runoff and other impurities. Water current or velocity can reduce the thickness of ice especially near a spring or outlet.