How far from Lake Michigan can “lake effect snow” occur?

Dear Tom,
How far from Lake Michigan can “lake effect snow” occur?
Tommy Lanston, Chicago Heights
Dear Tommy,
The great majority of lake effect snows that sweep off the south end of Lake Michigan head southeast into Indiana and do not affect Illinois. That is because lake effect snows are low-temperature events — the colder the air the better — and the very coldest air masses here involve southeast-bound invasions of arctic air. On occasion, though, air cold enough to generate lake-effect snow spreads across the area on northeast winds and at those times snow moves into Illinois. Heaviest within about ten miles of Lake Michigan, these snows diminish quickly to flurries that will sometimes spread as far west as the Mississippi River and as far south as central Illinois — about 175 miles from the lake.

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