For the second straight year, Mardi Gras revelers across south Louisiana will be braving chilly weather — but rain, at least, is unlikely.

A cold blast of air from Canada and the Arctic Circle sent temperatures across the region plunging by about 20 degrees in a two-hour span on Monday, which means Tuesday’s temperatures will begin in the 30s for morning parades, said Andrew Ansorge, a meteorologist with the National Weather Service in Slidell.

“It’s going to be a pretty raw, pretty nasty day,” state climatologist Barry Keim said. “It’s the kind of cold that cuts right through you.”

The afternoon will bring some, but not much, relief. In New Orleans, the afternoon high won’t get out of the upper 40s. In Baton Rouge, the morning will stay in the 30s and peak in the high 40s by the afternoon; Lafayette will follow a similar pattern.

Temperatures may feel colder than the numbers thanks to overcast skies and blustering winds, Keim said.

“For people who have outdoor plans, it’s going to feel very chilly,” Ansorge said. “It’s been a pretty nice Mardi Gras season up to this point, but just as Mardi Gras is coming to an end, so are the warm temperatures, for a few days.”

Keim advised revelers to bundle up and consider bringing an umbrella for a morning parade — but he added that by the afternoon, the chances of rain diminish.

New Orleans expected about 1/4-inch of rain on Monday afternoon and evening, but the rain should taper off in time for Fat Tuesday festivities, said Bob Wagner, a meteorologist with the National Weather Service in Slidell.

The weather system in question “developed a little quicker than it had looked like earlier in the weekend,” Wagner said, “and the rain and the front are mainly going to be (Monday) instead of Tuesday.”

Still, the ugly weather is an improvement over last year’s Mardi Gras, when some highways closed for several hours as temperatures stayed in the 30s, compounded by rain, Keim said.

The coldest Mardi Gras on record occurred Feb. 14, 1899, with a high of 38 degrees and three inches of snow that had to be cleared before Rex could roll through the streets of New Orleans, according to the National Weather Service.

Jim Mustian contributed to this report. Follow Daniel Bethencourt on Twitter, @_dbethencourt.