Making Snow with Hot Water and Other Frozen Phenomena
Much of North America is experiencing the coldest temperatures in twenty years. They call this a polar vortex, in which Arctic air currents sweep further south than usual. Today is supposed to be the coldest day of the vortex. For now. Temperatures fell so fast that reports came in across Canada of frostquakes, which occur when groundwater freezes so fast that it cracks the frozen ground. They make a lot of noise, but don't cause much damage. Other strange things occur when the temperature falls this far and this fast. See what they look like in an article I wrote for mental_floss.