SmogRank / Episodes / United States

Bad-air episodes in United States

42 times since January 2023, many cities in United States had air at least twice as dirty as their usual for the time of year on the same days. The largest reached 279 cities: North-eastern United States and Canada, June and July 2023.

2023

Each row: one bar per day, as tall as the number of cities counted that day and coloured by their median level; the number of cities; the highest daily reading and where. An episode is a run of days when many cities close to each other (four or more within 350 km on a day, 8 or more in all) each had a daily PM2.5 mean of at least 25 µg/m³ and at least 2 times their usual for that time of year. Found in our own measurements, not picked by hand. How we find episodes.