It’s official: Fall has begun

It’s hard to believe, but summer came to an end today.

The first official day of fall began at 4:02 p.m., which was the exact moment when the sun’s path crosses directly over the equator.

The changing of the seasons is due to the tilt of the earth, at 23½ degrees, and its orbit around the sun. During the summer, the northern hemisphere is titled towards the sun, allowing for a higher sun angle and longer days. This helps to warm areas above the equator.

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The opposite happens during the winter. It’s during the equinoxes, first day of fall and spring, that the northern and southern hemispheres both receive nearly the same amount of sunlight.

Moving forward into autumn, shorter days and longer nights will bring about a big change in temperatures.

Typical highs in the Miami Valley on the first day of fall should reach the lower 70s. In one months’ time that average daytime high will fall into the lower 60s.

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This decline in temperatures will continue well past the first day of winter (Dec. 21) until we reach our coldest temperatures in mid-January. By then the average daytime high is around the middle 30s.

Although cooler, the fall comes with some beauty.

It’s the seasonal switch that actually triggers leaves to start changing colors. During this time, chlorophyll, which is dominant in summer giving leaves their green tones, starts to break down and new colors are reveled. One of the interesting facts is that the vibrant colors revealed this time of year are actually the true colors of the leaves.

The vibrancy and duration of fall foliage is influenced by temperatures, sunlight and rainfall. For the brightest colors sunny conditions are needed as well as seasonal rainfall totals with cool, but above freezing nights.

McCall Vrydaghs is a WHIO StormCenter 7 meteorologist. Contact her at mccall.vrydaghs@coxinc.com or follow her on Facebook and Twitter.

WHIO StormCenter 7 Chief Meteorologist Eric Elwell will return next week.

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