For the second straight year, revelers will be braving chilly temperatures on Mardi Gras as New Orleans braces for a cold front expected to plunge temperatures into the 30s for early-morning parades.

The city will see a quarter of an inch of rain or more Monday afternoon and evening, though the precipitation should taper off in time for Fat Tuesday festivities, said Bob Wagner, a meteorologist with the National Weather Service in Slidell.

“People should not be counting on staying dry tonight,” Wagner said. “For the parades tomorrow, we’re not expecting much in the way of precipitation, but the temperatures will get everybody’s attention.”

Tuesday’s temperatures are not expected to get out of the mid to upper 40s.

“During the day tomorrow, it’s not going to be that wet, but it’s certainly going to be cold,” Wagner added. “Even though the thermometer says temperatures are in the 30s, it may feel even colder than that for those morning parades.”

Earlier forecasts had called for a near washout on Mardi Gras. But 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 this afternoon and this evening instead of Tuesday.”

With the mercury climbing into the 70s on Monday, the latest forecast called for temperatures to fall in New Orleans “20 to 30 degrees within the space of a couple of hours,” Wagner said, as the wet weather pushes through.

Winds could be a major factor Monday evening. Wagner said the city could experience sustained winds between 20 and 25 mph.

“We can’t rule out some thunderstorms,” he added.

In anticipation of the rain, city officials announced that the Krewe of Proteus will roll at 4 p.m. Monday instead of 5:15 p.m., while the Krewe of Orpheus will begin at 4:45 p.m. Monday instead of 6 p.m. In a slight change, both parades also will turn right at Canal Street from St. Charles Avenue, then continue along their normal routes.

The frigid forecast is reminiscent of last year’s water-logged holiday, when temperatures hovered in the 30s for much of the day and the city recorded more than one-third an inch of rain.

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

Follow Jim Mustian on Twitter @JimMustian