HOUSTON (NEXSTAR) — The last time there was a full moon on Halloween, the United States was still engaged in World War II. Now it looks like the stars – and the clouds – are aligning to allow most Americans to enjoy some added ambiance on October 31st, even if their trick-or-treat plans have been disrupted by the pandemic.

For many people, the Halloween full moon will be a once-in-a-lifetime event. The last time it occurred was in 1944, according to the Farmer’s Almanac. The next one isn’t expected to happen until 2039, NASA said.

Although Saturday’s moon will be a “blue” moon, it won’t actually appear to be blue. Scientists use the term to describe the second full moon of a given month, which only occurs about once every 2 1/2 years, NASA said.

According to the Farmers Almanac, the first full moon of 2020 howled onto the scene with January’s Wolf Moon on Jan. 10. And usually, we have one for each month, making the total 12 for the year. But on occasion, some months will have two full moons.

That’s the case for this month. There was a full moon on Oct. 1, known as the Harvest Moon, which usually appears in September. It is so named because it occurs closest to the autumnal equinox. The Sept. 2 full moon occurred too early to be known as the harvest moon.

The second is coming up on Oct. 31 — a Halloween Blue Moon. It is also called the Hunter’s Moon because it usually occurs in October, the month when traditionally game was fattened and preparations for winter began.

This year’s Blue Moon, which will turn full at 10:49 a.m. EDT, will be a rare Halloween treat.