Bryan Lambeth is a meteorologist with the Texas Commission on Environmental Quality. He says ozone season typically starts in March, but there wasn't enough of the right kind of weather last month.
"You have to have light winds, you gotta have warm temperatures, plenty of sunshine. There's plenty of emissions in the Houston area, so when the worst-case meteorological conditions occur, we tend to get high ozone forming in the area."
The number of ozone warnings in Houston has fallen in recent years, even with tougher EPA standards. Lambeth says in 2009, the TCEQ issued 38 ozone watch days in the Houston area, with 31 turning into warnings. He says those numbers vary considerably from year to year.
"It's possible we could see as many as 45 or maybe even 50 days this year, if we had a really bad year. Or, if it's a really quiet year, it might be even less than 30."
Lambeth says ozone watches and warnings typically do not affect the entire city or metro area. A detailed map of ozone levels in Houston is below, or can be viewed at http://www.tceq.state.tx.us/.