Storm Was a No-Show : The Two Hs, Hot, Humid, Will Prevail

Ominous thunderheads hovered over a humid Orange County on Tuesday, appearing for a while as though a wayward Midwestern summer storm had drifted this way.

However, the storm didn’t materialize, and those thunderheads left behind only a promise of heat, more clouds and fog. A 20% chance of rain today also was forecast by the National Weather Service.

In Santa Ana, Tuesday’s high was a muggy 98 with relative humidity of 43%. In El Toro, temperatures reached 104, with 41% humidity. A weak low-pressure system off San Diego contributed to Tuesday’s unsettled Southland weather, the weather service said.

The muggy weather combined with pollutants, prompting the South Coast Air Quality Management District to declare a stage-one smog alert in north Orange County at 2:15 p.m. Tuesday.

A stage-one alert occurs when air pollutants reach a level at which a potential health hazard exists, based on the Pollutant Standards Index scale of zero to 500. The PSI reading was 205 for north Orange County, where sensitive people, the ill, elderly and young were urged to curtail strenuous activity.

Weather service forecasters called for some late-night and morning low clouds and local fog today, giving way to variable high cloudiness.

But little temperature change was expected today and Thursday, with the mercury expected to reach from the 70s at the beach into the 90s inland.

The extended Southern California forecast for the coastal area over the Labor Day weekend called for a cooling trend with mostly fair skies, except for increasing night and morning low clouds and fog near the coast.

There is a slight chance of afternoon and evening thunderstorms on Friday. But otherwise, the weather should be fair and cooler.