North of Jackson, lows are expected to drop into the low teens with a wind chill below 10 degrees.
Meteorologist Jared Allen says some areas will stay at or below freezing until Tuesday.
On the coast, Harrison County Emergency Management director Rupert Lacy says about 150 people have shown up at cold-weather shelters run by nonprofits.
With frigid temperatures across Mississippi, communities are opening shelters and people are being told to keep an eye on their pets and elderly neighbors.
Jackson city spokesman Chris Mims says officials are expecting shelters to be full the next two nights.