Even if the leaves haven't yet begun turning where you live, Labor Day is over, school is back in session and fall is almost here. The official arrival of the season is the autumnal equinox, which occurs in the Northern Hemisphere this month.

After a hot summer , the September equinox marks a welcome shift in the seasons for many folks. But what exactly is an equinox? It's all about Earth and its relationship with the sun. Here's how to understand, visualize and celebrate the autumnal equinox.

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When is the autumn equinox?

This year, the autumnal equinox in the Northern Hemisphere falls on Monday, Sept. 22. If you want to be extra specific and mark it on your calendar, mar

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