An air-quality alert was issued in Philadelphia and its surrounding counties Wednesday, and a Code Orange advisory is expected again Thursday as smoke from Canadian wildfires has moved south. The haze mixed with the warmer temperatures has caused ozone levels to elevate, which can lead to issues for people with respiratory conditions.

While the city was at a Code Orange at one point Wednesday, the level was reduced to a Code Yellow in the afternoon. It's expected to return Thursday to a Code Orange, which is when the air quality is "unhealthy for sensitive groups," according to the Pennsylvania Department of Environmental Protection .

RELATED: What are the health risks of wildfire smoke? Here's how to limit your exposure

"On air quality action days, young children, the elderly

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