A warming trend this week should peak Wednesday with highs breaking 100 degrees in the East Bay, prompting the third Spare the Air alert this summer.

High temperatures stir up pollutants and smog, turning the air particularly unhealthy, said Lisa Fasano, a spokeswoman for the Bay Area Air Quality Management District, which issues the alerts. Tuesday was also a Spare the Air day.

When cooler temperatures move into the region Thursday and Friday, the air quality should improve.

via Bay Area faces another Spare the Air day – SFGate.