Five Oregon cities set all-time records for air quality in the past week, due to smoke from dozens of wildfires.

Portland, Eugene, Bend, Medford and Klamath Falls surpassed the mark according to a study of current and historical air quality index records by the state Department of Environmental Quality. The Lane Regional Air Protection Agency also contributed to the study.

The index, first developed in 1976, ranks air quality. The version used by Oregon has five steps: good, moderate, unhealthy, very unhealthy and hazardous.

All five cities set new records for poor air quality, each surpassing marks set in September 2017 when the state experienced major wildfires.

Prior to the current fires, Medford was the only Oregon city to have experienced a “hazardous” air quality level, one day each in 1987 and 2017.

Last week, Eugene had five hazardous days. Bend and Medford had three. Portland had two, and Klamath Falls had one. Portland has never recorded a day in which the air quality index reached “very unhealthy.” It surpassed that mark twice last week.

On Saturday night, an EPA-monitored station in Madras had the highest air quality index in the United States. 

The Department of Environmental Quality said shifting winds and possible rain could improve air quality in parts of the state by Thursday. But a return to “good” levels that were common before recent wildfires began burning will take longer. 

State air quality data and maps can be found at http://oregon.envi-das.com/home/map