Between 2003 and 2006, the San Joaquin Valley was nearly wall-to-wall with bad-air days each August. Only six August days in those years didn’t breach the ozone standard.
This August, there already have been six good days, and the month isn’t even two weeks old. For me, it’s even a little eerie to see days like Thursday when the highest ozone reading was about what I’d expect on a warm, sunny April day.
The temperature has dropped into the 90s and that helps, because ozone forms better on hot, sunny days. But there were plenty of August days in the 90s back in 2003 or 2004 when ozone exceeded the standard.
Meteorologists have told me the air overhead is moving and mixing a lot this month. Ozone forms best on hot, sunny days that are stagnant, so maybe the air movement is helping.
Last August, there were only five days without exceedances. In 2011, there were only two. To me, the break this year just seems odd.
But don’t be lulled. August and early September can turn brutally hot and stagnant. And with school back in session and more vehicles on the road producing ozone-making gases, the air can turn corrosive quickly.