According to AirNow.gov, the Air Quality Index (AQI) as of 8 a.m. in Pittsburgh had reached 238 — code purple.
In other words, extremely unhealthy for any group, especially those with sensitivities. AQI levels in greater Philadelphia were at 162.
Residents were being urged to stay inside.
Thursday was expected to be a hazy day with highs in the mid-80s.
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