Dear Tom,
The northern lights were recently visible across the upper Midwest. Are they ever visible in Chicago?
—Vanessa C. Bolingbrook
Dear Vanessa,
They are, but, on average, the northern lights are only visible in Chicago about once every two years, and when they do occur, they are hard to see because of light pollution. Away from the city, in dark rural areas, they might be visible few times each year. They have been sighted in all 50 states and as far south as northern Mexico, but your best bet is to travel north, where the frequency of auroral displays increases dramatically, peaking with as many as 100 annual sightings in Alaska and northern Canada. Autumn and winter are the most common times for viewing the aurora borealis as the period of darkness increases from its summertime minimum.