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Fall foliage exhibited at Greenbrier State Park on October 30, 2017 in Boonsboro, Maryland (Katherine Frey / The Washington Post)
The summer had a hard time letting go in September. In the DC region and many parts of the country, The unrelenting humidity made us sweat for weeks and signs of falling were rare.
But if you're ready to put on your favorite sweater with a cup of hot cider in your hand, time is at your side. The autumn equinox arrives Saturday at 21:54 Eastern, which means that cooler weather is inevitable.
The autumnal equinox, traditionally considered the first day of autumn, occurs every year around September 22 or 23. This is the exact moment when the sun appears directly above the equator of the Earth.
After the equinox, direct sunlight shifts to the southern hemisphere, where winter ends and spring begins now. In the northern hemisphere, we will see that daylight will continue to decrease for three months until the December 21 winter solstice.
On the equinoxes, none of the hemispheres of the Earth is inclined toward or away from the sun. (National Meteorological Service)
Every year around the autumn equinox, we lose the light of day during our fastest clip of the year. The district now loses 2 minutes and 30 seconds of light a day. In the northern United States, cities like Minneapolis and Seattle see more than three minutes of sun disappear with each passing day.
The change of sunlight is the main reason why the trees burst in bright shades of red, orange and yellow before dropping their leaves for the winter. (To find out when fall foliage will peak in your area, check out this excellent reference.)
We still have a few days left before entering the dark half of the year, when the trees start to react to the light of day. Even if the equinox literally means "equal night" in Latin, the two hemispheres of the Earth still have more than 12 hours of light on Saturday. One of the reasons for this is that the Earth's atmosphere is refracting or bending, causing the sun to appear higher than it is in the sky.
In the district, the sunrise and sunset on the equinox are respectively at 6:56 and 19:05, which gives us 12 hours and 9 minutes of day. It is only on September 26 that sunrise and sunset will fall exactly 12 hours apart at 6:59 am and 6:59 pm.
As the nights get longer and the sun falls lower in the sky, temperatures begin to drop quickly. The district's high average temperature, which is now 77 degrees, drops to 64 degrees at the end of October. The average low temperature drops below 60 degrees on September 24 and will not return until the end of May.
As if nothing had happened, Mother Nature could offer you a first taste of cool and autumn weather next weekend. The latest forecasts from the National Oceanic and Atmospheric Administration's Prediction Center show sub-normal temperatures in the central and eastern United States at the end of October.
(NOAA)
If you're expecting a real autumn taste after our long swampy summer, this forecast will surely bring a smile to your face.
You can finally indulge in this latte of pumpkin spice, and it will really feel good.
Read more:
Say goodbye in the summer: seven cards that explain the autumn equinox
The leaves begin to show signs of autumn. Here's why they change.
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