What are the long-term odds of a white Christmas?
Christmas is less than two weeks away, and the question of “will there be a white Christmas?” is beginning to come up. We consider a “white Christmas” to be one with at least an inch of snow on the ground on Christmas Day.
While it’s hard to give a simple “yes” or “no” since a lot can happen between now and then, the general weather pattern is one that keeps highs above freezing through at least the end of next week. There have been some consistent signals of colder weather arriving just before Christmas. Precipitation is harder to pin down, but there aren’t any real snow chances until next Friday at the earliest, and even that is questionable this far out. We’ll have a better sense of this as time goes on. At this point,
we get a white Christmas, it’s probably going to be down to the wire.
Regardless of whether or not there’s snow on the ground on the 25th, it’s important to put all of this in context. The long-term odds of a white Christmas in much of the state is actually close to 50-50. Northern Iowa, not surprisingly, has higher odds – it’s about six or seven out of every ten there. Meanwhile, southern Iowa has lower chances over the long-term – about three or four out of every ten years.
These are the climatological chances of a white Christmas in several of the long-term climate observation sites in eastern Iowa. This is done by taking the most recent 30-year period of records and seeing how many of them had an inch of snow on Christmas Day. So, if 15 of the years did, then it’s a 50% chance.
Cedar Rapids: 47%
Iowa City: 44%