Dear Tom,

My "trick or treat"-age son saw a Discovery Channel program on how animals in Yellowstone National Park cope with deep snow in winter. Now he is worried about snow here on Halloween. What is the likelihood?

—Irene Lohr, south suburbs

Dear Irene,

Your son need not be concerned about snow on Halloween because Chicago snowfall statistics for Oct. 31 speak strongly against its occurrence. For the 127 Halloweens for which we have snowfall records (1884 through 2010), there has never been an accumulating snow. Snowflakes were reported on 6 of the 127 Halloweens, or an average of about 1 in 21 years, but never any accumulation.

But do prepare for chilly weather on Halloween. The high temperature was in the 50s or lower on 3 out of 5 Halloweens. And it's rained on about 1 out of 3 Halloweens.