This Friday the 13th, a cratered Jack-O-Lantern will light up the sky.

Even more than the pumpkin spice latte, the harvest moon officially marks the beginning of fall. The days grow shorter, the air gets brisker and a glowing full moon kicks it all off. Here's what it is, when you can see it and why it's teenier this year.

What's a harvest moon?

A harvest moon is a full moon that usually occurs around the autumnal equinox (September 23, the first day of fall!) but sometimes laze into October in the Western Hemisphere.

A harvest moon rises about 25 minutes after the sun sets in most of the northern US, NASA said, 25 minutes earlier than a typical moon. This brings extra light in the evenings.

What causes it?

The moon's positioned at the "most shallow angle" with the eastern horizon, the Farmer's Almanac said. This shortens the period between the time the sun sets and the moon rises.

And like any full moon, the sun and moon are opposite each other, so the sun cranks up the moon's brightness.

Why is it called a 'harvest moon'?

Thank farmers. Those extra 25 minutes of sunlight extended harvesting time for farmers, so they could continue their picking later into the evenings. And at the right time, it kinda looks like a big, glowing pumpkin.

Why is this one special?

It's mini! This year's harvest moon will occur during the apogee, or the point in the moon's orbit when it's farthest from Earth. As a result, it'll appear 14% smaller than a typical full moon, the Farmer's Almanac said.

Why does it look reddish-orange sometimes?

Like the sun when it sets and rises, the moon looks redder the closer to the horizon it gets. That's because red light waves pass through the atmosphere. So when it makes its descent through the sky to the horizon, most of the blue light waves have been removed, according to the Cornell University astronomy department.

When can I see it?

The best time to get a peek is when the micro moon reaches its peak at 12:30 a.m. Saturday. The full harvest moon will rise just after sunset, though.