With 10,000 customers still without power on Wednesday after Monday’s storm, most of them in the south and southwest suburbs, ComEd said some might not have electricity until later this week.

The utility said it had 600 crews deployed to restore power and expected most would have electricity by Wednesday night.

ComEd said the south and southwest suburbs were hit harder by power outages than the rest of the Chicago area. Strong winds, which in many areas reached 75 mph, snapped tree branches and downed power lines, according to ComEd.

The National Oceanic and Atmospheric Administration classified Monday evening’s swath of severe weather as a derecho, a system typified by a widespread and lengthy windstorm associated with a band of rapidly moving thunderstorms. The NOAA said a derecho in the Chicago area occurs, on average, once a year.

The storm sent a towering oak tree, estimated to be two centuries old, smashing into the home of Jacques and Doreen Lopez in the 9600 block of 50th Court in Oak Lawn.

The couple said they were relocating to a hotel while an engineer determined whether the Cape Cod, which they moved into after their wedding 27 years ago, was structurally sound.

Doreen is worried because there’s a large crack in a living room wall near the front door.

“We have no idea yet what he’ll say. It would be a shame if he says it isn’t safe,” she said.

Rainwater was seeping into the house Wednesday from morning showers because a tarp could not be put completely in place on the house before nightfall Tuesday, Doreen said.

She said Homer Tree Service arrived about 6:30 p.m. Tuesday and was able to remove the tree from the house.