The start time for the MLB game between the New York Mets and the Phillies on Thursday in Philadelphia was moved up an hour due to air quality concerns because of wildfire smoke from Canada and northern Minnesota, and an MLS game in Chicago was postponed.

Heavy, pungent wildfire smoke darkened skies in the U.S. from the Great Lakes to parts of the East Coast, reducing visibility and prompting warnings that breathing the air outside could be dangerous.

Officials in many cities urged residents to stay inside or wear masks outside as air quality reached unhealthy to hazardous levels, meaning it’s unhealthy for anyone, regardless of health conditions. The National Weather Service said a lingering high pressure system has trapped the smoke close to the ground.

The Philadelphia region is experiencing smoky and hazy skies. The game’s start was moved to 6:10 p.m. EDT from 7:10 p.m. It is the only game on the big league schedule coming out of this week’s All-Star break.

“It’s definitely different,” Phillies first baseman Bryce Harper said on ESPN during the broadcasting of the game. “Not the greatest idea, I guess, to come out here and play in this type of weather, but we’re doing it.”