The Minnesota Department of Transportation is warning motorists to watch out for roads that might buckle without warning.
MnDOT spokesman Kent Barnard said the heat and humidity had caused pavement to heave on some Twin Cities metro highways.
Monday afternoon lanes were closed in I-94 in Minneapolis and St. Paul. Barnard said heat damaged roads in more than 20 places.
Barnard said he has not heard of accidents associated with buckling pavement. But he'd heard reports of damage to cars.
Older concrete highways are more prone to heave up, as debris fills the cracks between the panels, leaving no place for the pavement to expand.
"The natural expansion places are filled up and so there is no place for that pavement to expand," Barnard said. "And the stress of that expansion looks for the weakest area. It could be another crack in the pavement or it could happen real close to where the expansion joint actually is."
There's no way to predict exactly where pavement will heave. Barnard said motorists should watch the road and not tailgate.
While the roads are still prone to buckle yet through the evening, Barnard said they should be better by the Tuesday morning commute.