Update: All of Pennsylvania is under a Code Orange air quality alert on Friday. The weather pattern causing the poor air quality is expected to move out of Pennsylvania over the weekend.

(WJET/WFXP/YourErie.com) — The City of Erie announced that Erie County has been listed as Code Orange by the United States Air Quality Index as of Thursday morning.

According to the Air Quality Index website, Erie County’s air quality index (AQI) was listed at 126 Thursday morning, sitting right in the middle of the Code Orange range of 100-150 AQI.

All of Pennsylvania was under a Code Red Air Quality Alert Wednesday.

Wednesday evening, Nexstar station WPHL reported Philadelphia was considered to have the worst air quality out of any major metropolitan area in the United States, according to air.gov. As of 10 p.m., the air quality in Philadelphia was at 447, which is considered hazardous.

People with heart or lung diseases, older adults, children and teens are advised to take steps to avoid exposure.

A full interactive map is available at AirNow.gov.