Dear Tom,

Why doesn’t it thunder during a snowstorm?

Tommy Smithson,
Gary, Indiana

Dear Tommy,

At Chicago, winter weather is typified by stratoform (horizontal) cloud layers in the atmosphere. These layers are generally stable and do not create an electrical charge differential. As a result, lightning and thunder are rarely part of the winter scenario. On occasion, though, moist and unstable Gulf air works its way as far north as Chicago. Such air can touch off a thunderstorm, but usually temperatures are above freezing and the precipitation is rain. On rare occasions, unstable Gulf air overrides more dense colder air at the surface. This forces the moist air higher into the atmosphere and can touch off “thunder snow,” a bona fide thunderstorm that can produce intense snowfall, often a few inches in just a matter of minutes.