Does NC’s halo moon this week mean snow is coming soon? What experts say

A photo of a halo moon over North Carolina was posted on social media this week, and some were quick to ask if this means snow is coming soon. Does it?

We asked the experts, and here’s what they said.

What’s a halo moon?

A halo moon is a moon with a variety of bright circles or arcs around it.

The circles are caused by the refraction of light by ice crystals that are suspended in the earth’s atmosphere, said Gail Hartfield, a meteorologist with Raleigh’s National Weather Service.

Suns can also have halos around them.

Does a halo moon mean snow is coming?

Not exactly, though there are a few factors that might bring about halo moons more often in cooler months:

▪ Fine ice crystals: Halo moons are associated with high cirrus clouds, which are composed of fine ice crystals. That’s what causes the refraction, which produces the halo.

Cirrus clouds often spread in — and gradually thicken with lowering cloud bases — ahead of storm systems during the winter months.

▪ Summer storms disrupt clear nights: You have a greater chance of seeing the moon during cooler months, as summertime often brings late-day or evening storms.

“As they fall apart and weaken during the late evening or early overnight hours, they can leave behind residual mid- and high-level cloudiness over the area that might keep people from seeing a clear picture of the full moon during those warmer months,” Hartfield said.

▪ In summary: Halo moons aren’t predictive of snow or a telltale sign that snow is definitely on its way, but halo moons are common to spot in the winter months.

Snow is much more likely during these cold seasons, so snow may be on its way already — but not because of the halo moon.

Will North Carolina see snow in December?

Weather lore in the Farmer’s Almanac has taught many of us that a halo moon means snow is coming soon. But NWS Raleigh meteorologists caution against getting weather predictions from the Almanac.

“Typically, the observation of a lunar halo brings some form of precipitation within the next 24 to 36 hours, but not all the time. There are more factors in play to produce snow than just the presence of ice crystals 25,000 feet in the air the day before precipitation moves in,” said meteorologist Aaron Swiggett.

But the amounts, intensity and phase of precipitation (which could be snow, ice or rain) all vary widely with each lunar halo spotting.

“It’s hard to get snow this time of year, especially in December. We get most of our snow in January and February,” he said.

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