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Why the equinox doesn’t mean EXACTLY equal day and night in southwest, central Virginia

The equilux happens Saturday, Sept. 25

Autumn. (WKMG)

ROANOKE, Va. – In elementary and middle school, I remember being taught that the equinox meant that we saw 12 hours of daylight and 12 hours of darkness. While that’s close, it’s not exactly right. (I know...I’m splitting hairs here.)

The equinox happens when the sun’s rays are directly above the equator, signaling the beginning of either astronomical fall or spring in the Northern Hemisphere.

Autumnal equinox - 2021

The autumnal equinox happened Wednesday at 3:21 p.m. local time. In our area, we still had roughly 12 hours and nine minutes of daylight.

Why is that the case?

This has to do with the way that sunlight is measured and how light is refracted (bent) in the atmosphere. This bending of the sun’s rays causes it to look as though the sun’s disk is above the horizon, when it’s really still below that point.

So on the equinox, the day is a bit longer the farther north you go, because the sun takes longer to rise the farther north you go this time of year.

The equliux, when we see almost exactly 12 hours of daylight and 12 hours of darkness, occurs this Saturday, Sept. 25.

Equilux happens on Saturday, 9/25/2021

About the Author:

Meteorologist Chris Michaels is an American Meteorological Society (AMS) Certified Broadcaster, forecasting weather conditions in southwest Virginia on WSLS 10 News from 5 a.m. to 7 a.m. weekdays on Virginia Today.