The science of snowflakes: See how they form and why no two are ever alike Snow is made up of trillions of tiny ice crystals that make snowflakes, with not one alike. Here's how they form.

How do sleet and freezing rain form? Sleet and freezing rain form because of a "warm-air sandwich" in the atmosphere above our heads (see graphic, below). Precipitation starts as snow in the cold ...

How do sleet and freezing rain form? Sleet and freezing rain form because of a "warm-air sandwich" in the atmosphere above our heads (see graphic, below). Precipitation starts as snow in the cold ...

How do snow devils form? Similar to a dust devil, a snow devil is created by wind shear - winds blowing in opposite directions near the ground level of the atmosphere.

Even still, January's snow was unusual simply because of its range from Texas to Florida, Lanza said. There likely have only been a couple other similar snowfalls in our region.

A winter storm sweeping through the southern U.S. this week dumped snow at levels many in those regions have never seen before, but how does it compare to Chicago? The answer is surprising.