The snow and sleet have stopped falling and traffic has started moving again in Atlanta following the crippling winter storm.

However, bitterly cold temperatures are refreezing the slush left behind by the mess.

At Hartsfield-Jackson Atlanta International Airport, more than 400 flights in and out were cancelled on Thursday, according to flight tracking service FlightAware. The rippled effect has canceled dozens of flights in Houston.

It’s not just airports wary of more trouble. Heeding the freeze warnings, school districts and state and local governments stretching from northwest to coastal Georgia announced that offices and classrooms would remain closed on Thursday.