Fall Equinox Comes on Mercer Island on Saturday

Today is the last day of summer 2012, and fall is just hours away — that means another fall (or autumnal) equinox is coming.

But what is the autumnal equinox? 

Equinoxes fall on the halfway point between solstices and occur, according to the Washington Post, "when the sun crosses the equator and day and night are of roughly equal length, everywhere in the world."

The nearly equal 12 hours of light and darkness can be attributed to the Earth's lack of an axial tilt on the day of the equinox. In fact, the word equinox is derived from the Latin words aequus, meaning equal, and nox, meaning night.

On Mercer Island, according to sunrisesunset.com, the sun will come up at 6:56 a.m. and set at 7:08 p.m on the autumnal equinox. As you notice, that is not actually a perfect 12 hours of light and darkness. As timeanddate.com reports, this is because of issues such as light refraction and other reasons.

See ya next year, summer. Hello fall, and happy autumnal equinox!

Here's the weekend forecast according to the National Weather Service:

• Tonight: Cloudy, with a low around 54. Light and variable wind.
• Saturday: Areas of drizzle before 11am, then a chance of showers after 11am. Patchy fog before 11am. Otherwise, cloudy, with a high near 66. Calm wind.
• Saturday Night: A 30 percent chance of showers before 11pm. Cloudy, with a low around 53. Light and variable wind.
• Sunday: Mostly cloudy, with a high near 69. Calm wind becoming northwest around 5 mph in the afternoon.
• Sunday Night: Mostly cloudy, with a low around 53. North northwest wind around 6 mph becoming calm in the evening.