Range of temperatures required for snow

Dear Tom,
What is the usual range of temperatures necessary for it to snow?
Beola Lenard, Bettie S., Patricia L., Evergreen Park
Dear Beola, Bettie and Patricia,
Ice crystals (that eventually clump into snowflakes) form in clouds only
when water vapor condenses in a below-freezing temperature environment.
Condensation in above-freezing temperatures results in water droplets and,
ultimately, rain. Air temperatures at ground level are sometimes a little
above freezing (but rarely above 40 degrees) when it is snowing because
snowflakes, falling from subfreezing air above, do not have time to melt
before they make it to the ground.
There really is no lower temperature limit at which snow can occur, though
Chicago's biggest snowstorms usually occur with readings in the 20s. Nearly
an inch of snow was measured at O'Hare Airport on Jan. 10, 1982, with the
temperature around 15 degrees below zero.