Ozone usually is a summertime air problem, but the ozone standard already has been breached twice in the San Joaquin Valley.

The goal is zero violations to clean up summertime air. That goal was gone before the first day of spring.

Both violations happened last week in Maricopa in southwest Kern County. They are the first March violations since 2007. A late-winter warm spell gets most of the blame.

At the same time, it's worth mentioning that the usual ozone suspects -- Fresno, Clovis, Bakersfield and Sequoia National Park -- are not violating the standard yet.

The point is that it's hard to escape ozone violations in the 25,000-square-mile San Joaquin Valley when nature turns up a little heat.

Pollutants are naturally trapped in the Valley's bowl, and they move around. Somebody somewhere winds up with a little more ozone.

Ozone is a corrosive gas that forms in the presence of sunlight and heat. Two gases are needed for ozone. One is oxides of nitrogen from combustion sources, such as cars and trucks. The other is volatile organic compounds -- think of vapors from gasoline, solvents and dairy waste.

When people breathe ozone in high concentrations, it can trigger asthma and bronchitis. But it also corrodes healthy lungs and skin.

The Valley's ozone is among the worst in the nation.

But the region's run of five years without a March violation is memorable if only because such early season problems were pretty common a few years ago.

March violations happened every year between 2001 and 2004. In 2004, there were nine violations. That's more than many cities around the country in August, the peak of the ozone season.

The Valley averaged 155 violations each year from 2001 to 2004, but the totals have fallen recently. From 2008 to 2012, the average was 105.

Temperature records fell all over the state

Meteorologist Steve Johnson, a private consultant in the Fresno area, posted a list of California records set on a warm Wednesday last week.

The list was topped by Fresno's 85 degrees, which broke the 2007 record for the day by one degree. Burbank broke its record by eight degrees.

From reading the list, it's clear 2007 was pretty warm, too. But there are also some very old records that were broken. The Riverside record was more than a century old.

Also, if warm weather continues, the snowpack in the Sierra Nevada will come rolling down sooner than usual. The snowpack is about 60% of average right now -- better than last year when it was about 45% as spring began in last March.