Arkansas Storm Team Blog: Fall has officially arrived

While it may not feel like fall outside, that doesn’t mean it isn’t here. Fall officially begins on Monday, September 22. To be even more specific, the fall equinox occurs at 1:19 p.m. C.D.T. on Monday.

On the fall equinox, there are nearly equal lengths of time in daylight as compared to time in darkness across Earth’s latitudes. There are only two days a year when time in daylight and time in darkness are equal in 24 hours, and that’s the fall equinox and the spring equinox. This is due to Earth’s axial tilt, which, on the equinox, isn’t tilted towards or away from the sun. The sun is directly overhead the equator in the middle of the day during the equinox (this occurs at 1:19 p.m. C.D.T. this year). The Earth’s tilt is the reason for the seasons.

The fall equinox can occur between September 21 and 24 each year due to Earth’s orbit around the sun. Earth’s orbit isn’t completed in exactly 365 days, or 1 calendar year. Instead, it takes the Earth about 365.24 days to orbit around the sun. This is not only why solstices and equinoxes aren’t always on a fixed date each year, but also why there’s a February 29 every 4 years.

Meteorological fall, in contrast to astronomical fall, began on September 1. Meteorological seasons are broken into 3-month periods that are mostly based on climate, but also provide easier record-keeping for meteorologists. Astronomical fall begins on the fall equinox and ends on the winter solstice. This year, the winter solstice occurs on December 21.