Fall has begun but the summer heat hasn't ended - WMC Action News 5 - Memphis, Tennessee

Fall has begun but the summer heat hasn't ended

Temperature trend for the next few days Temperature trend for the next few days
(WMC) -

Fall has arrived!  

The Autumnal Equinox, which took place at 9:21 a.m., marks the moment the Sun crosses the celestial equator or the imaginary line in the sky above the Earth’s equator and the Earth begins its tilt away from the sun. The process is vise versa during the spring equinox.  

That fall tilt takes us away for the sun's direct rays, allowing a cooler pattern to take hold of the northern hemisphere and ultimately transition to winter. It's just the opposite in the southern hemisphere, where that part of the planet now begins its transition to more direct rays of sun and the summer season.

Thursday marked the first day of autumn, but you wouldn't have known it by the thermometer. The first day of fall ended up being warmer than the last day of summer as the afternoon high soared to 95 degrees in Memphis and temperatures all across the Mid-South climbed into the low to mid nineties.

The average high temperature for September 22 is Memphis 83 degrees, which is twelve degrees cooler than the high for the date this year. A couple of factors contributed to the warm weather for the start of fall.

  • First, there is an abundance of dry air in place across the Mid-South, and dry air has a tendency to warm quickly during the day and cool rapidly at night--as has been the case for much of the week.
  • Second, high pressure has been firmly entrenched to our northeast. That high pressure forces air to the surface. The compression of that air has a  heating effect. Cloud cover is also limited, since moist air cannot rise to condense to form clouds.
  • Third, the soil is very dry. The month of September has been very dry, with total monthly rainfall only amounting to sixty-seven hundredths of an inch, which is just under an inch and a half below average. The dry ground absorbs more incoming solar radiation and radiates more heat into the atmosphere contributing to warmer temperatures during the day and at night.

As is stands now, this pattern will continue through the weekend, but there looks to be a break in the pattern next week. A cold front will move south out of the northern tier of the U.S. Monday and into the Mid-South. A Canadian high will build in behind the front, ushering in a much-needed shot of cooler air as we get into Tuesday and remaining for much of the week.  

Rain chances will be limited here in the WMC Action New 5 coverage area, since there won't be much moisture in place in advance of the cold front.  But, just to our west, there could be flooding as a surge of Gulf moisture is expected from Louisiana, Texas, central and western Arkansas, and the Central Plains. We do expect to get some rain from the system but our biggest benefit will come from the cooler temperatures.  So brace yourself for a little more heat, but know that there are more seasonal temperatures headed our way.  

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