About 8:30 this morning, Eastern time, we reached a milestone on the way back to the warmth of summer. At that time, officially called the vernal equinox, the sun was directly overhead at a point on the equator, and spring officially began.

What does this mean for you and me? To gauge the progress of the seasons for yourself, watch the sun set one night this week, and note its position on the horizon. If you view the sunset from that same spot for the next six months, you'll notice that the sun will always set farther to the north of where you observed it set this week. And the farther north the sun is in the sky, the more direct sunshine we get. In practical terms, each day for the next six months will have more daylight than darkness.

By the way, the time and even the date of the vernal equinox varies from year to year because the number of days in a year isn't a whole number. Spring can arrive as early as the morning of March 19, or as late as the afternoon of March 21.