Weather Blog: Don't confuse equinox with equilux

By Jamie Martin, Meteorologist
Last Updated: Wednesday, September 28, 2016, 4:54 AM EDT

You've heard about the equinox. But do you know about the equilux?

  • Equilux is often confused with equinox
  • We just experienced autumnal equinox
  • Monday, Sept. 26 was equilux in Orlando

A common misconception about the equinox — the official start of spring and fall — is that it's when the length of daylight and night are equal.

But that's usually not the case.

The equinox occurs when Earth passes a particular point in its orbit around the sun; it’s not defined by the local length of the day.

Sunrise and sunset were both at 7:16 on Monday, Sept. 26, in Orlando. That day — when it has the closest amount of equal time with the sun above and below the horizon — is known as the equilux. Exact sunrise/sunset times can vary due to one's location.

In the fall, the equilux occurs a few days after the equinox; in the spring, it's a few days before it.

Because the sun's rays are bent by the Earth's atmosphere, the sun appears higher in the sky than it actually is. This is one of the contributing factors why we don't see exactly 12 hours of day and night on the equinox. That occurs a few days after the autumnal equinox and a few days before the vernal equinox.

But don’t focus on equal amount of sun and darkness — just enjoy the fact that we might start seeing cooler and drier air soon here in Central Florida. Enjoy the fall!