COLUMBIA, Mo. – Are you dreaming of a white Christmas? If you live in Missouri, you might need to adjust your expectations.

The official definition of a white Christmas is an inch or more of snow on the ground on Christmas Day, said Pat Guinan, climatologist for University of Missouri Extension’s Commercial Agriculture Program.

You have about a one in three chance of a white Christmas if you live in northern Missouri, Guinan said. “In mid-Missouri, the chance for snow on Christmas happens about once every four to five years, and in far southern Missouri you may go 10 years before your Christmas is white.”

If you want better odds, you may need to leave the state.

“You have to go north or higher up,” Guinan said. The upper Midwest and far northeastern states like Maine, New Hampshire, Vermont and upstate New York have a high likelihood of experiencing a white Christmas. The western mountain states and Alaska have good chances too.

“Back in 2000 there was a nice snow blanket covering most of the state,” he said. “In 2002 there was a good area of snow across the state. Then in 2010, there was a good snow blanket across the northeastern half of the state.”

Will Missourians see a white Christmas this year?

“A storm system is developing to the southwest, and there’s a decent chance parts of Missouri will see a white Christmas for 2013,” Guinan says.

Any snowfall will likely stick around, he said. Cold air is coming, keeping temperatures low through Christmas.