Dear Tom,
I always get these mixed up. What’s the difference between an equinox and a solstice?
Cindy Lehrman

Dear Cindy,
Four days each year are especially noteworthy as the Earth revolves around the sun. The summer solstice occurs about June 21, when the sun is directly overhead at its northernmost latitude (23.5 degrees N). It is the first day of astronomical summer and the day with the most sunlight in the Northern Hemisphere. The winter solstice, about Dec. 21 when the direct rays of the sun reach their southernmost position (23.5 degrees S), marks the start of astronomical winter and gives the Northern Hemisphere its least amount of daylight.

The equinoxes are the two dates when the overhead sun crosses the equator. The vernal equinox, about March 21, marks the onset of spring; the autumnal equinox, about Sept. 21, heralds the start of fall in the Northern Hemisphere. This year the autumnal equinox will occur 8:04 pm CDT on September 22.