4 Things to Know About Fall Equinox.

Today is the last day off summer and a hot one too, high 89.  That’s 8 degrees above the average high of 81. Tomorrow morning the fall equinox begins but it won’t feel much like the first day of autumn.  I’ll tell you about our hot first few days of autumn in a moment but first here are four things to know about the Autumnal Equinox.



  1. The astronomical calendar says fall officially begins at 9:21 AM Thursday morning in Middle Tennessee. That’s when the sun shines directly on the Earth’s equator, bringing almost the same amount of daylight and darkness around the globe.
  2. The word equinox is formed from two Latin words.  “Equi” means “equal” and “nox” means “night”.  The equal is describing the fact that the amount of darkness and daylight is almost the same on this day.
  3. The reason the amount of daylight and darkness are not exactly 12 hours has to due with sunrise and sunset.  You see “sunrise” is defined as the moment the upper edge of the sun’s disk becomes visible above the horizon, not when the center of the sun is visible. Likewise, “sunset” is defined as the moment the Sun’s upper edge, not the center, disappears below the horizon. The amount of time it takes to complete sunrise and sunset is added to the day and subtracted from the night. So it’s 12 hours of each, give or take a few minutes.
  4. While fall starts here, September 22 is the beginning of spring in the southern hemisphere, the vernal equinox. So while the weather will be getting cooler here, it will be getting warmer there.


Now that we know all that, the weather will be anything but fall-like the rest of the week. The ridge of high pressure will keep things hot and dry through the weekend.  Afternoon highs will be near 90 and overnight lows in the mid 60s.


A cold front will move in the beginning of next week. Right now there is a chance of isolated thunderstorms on Monday.  The greater chance of rain will be on Tuesday and Wednesday.  But the best part!…by Wednesday we could have lows in the 50s and highs in the 70s.  Perhaps this will bring an end to the exceptionally hot trend.

I’ll have the forecast update on Channel 4 News at 10 PM.

Lisa Spencer

posted 9:10 PM


About Lisa Spencer

Lisa Spencer is the chief meteorologist at WSMV Channel 4 Nashville. You can catch her weathercasts weekdays at 4pm, 5pm, 6pm, 6:30pm and 10pm.
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