New York City’s education department canceled all outdoor activities Wednesday, as wildfire smoke wafted from Canada and created unhealthy air conditions across a swath of the Northeast.

Recess, Public School Athletic League sports competitions, and outdoor field days were all canceled, Nathaniel Styer, an education department spokesperson, wrote on Twitter late Tuesday evening. Schools were encouraged to move those activities indoors if possible.

“This is a developing situation and will communicate updates as they come,” Styer wrote.

Health authorities have warned that the smoke laden air is particularly harmful to more vulnerable groups, including young children and people with existing health conditions and breathing issues. They have urged people to stay indoors when possible and avoid strenuous outdoor activities.

Styer noted that schools were advised that “special attention be made to vulnerable students and staff populations.”

City officials said that the region’s air quality was expected to improve Wednesday morning but would deteriorate again in the afternoon and evening.

“Currently, we are taking precautions out of an abundance of caution to protect New Yorkers’ health until we are able to get a better sense of future air quality reports,” Mayor Eric Adams said in a statement. “These recommendations may change based on updated air quality conditions that come in, but, in the meantime, we recommend all New Yorkers to take the precautions they see fit to protect their health.”

Officials said that people who need to be outside should wear a high-quality N95 or KN95 mask.

Air purifiers can also help reduce the harmful effects of wildfire smoke. During the coronavirus pandemic all classrooms were outfitted with those devices, though schools have not always used them consistently as the virus has receded. Experts also previously questioned whether the devices the city purchased were the most effective available.

Read the full article about wildfire smoke by Alex Zimmerman at Chalkbeat.