Colder weather means ice will begin covering many of Montana’s waterways and tempting winter anglers to start ice fishing. Anglers should keep in mind that from early December through mid-January, ice begins to firm up and may melt when temperatures fluctuate. That means ice that was safe yesterday may be a death-trap tomorrow. Whatever the weather, it’s best to test the condition of the ice before venturing onto it. The ice’s thickness depends on a number of factors: currents, inflows from streams, water depth, underwater springs and stumps or other features protruding through the ice. Slight changes in any of these can lead to rapid changes in ice conditions. The best method for determining ice thickness is to carry an ice spud and test the thickness when walking onto a frozen lake, especially if no one has been on the lake recently.