Winter Weather Pays an Early Visit : Forecast Is for More Cool Temperatures, Chance of Rain

A 20% chance of rain, cloudy skies, gusty winds and cool temperatures highlighted a weather prediction Tuesday that forecasters commonly reserve for winter forecasts.

“This is a very, very unusual weather pattern that I haven’t seen the likes of in a long time. It is not a phenomenon we normally see now--it is not normal until Halloween or Thanksgiving,” forecaster Wilbur Shigehara said.

Today’s temperatures are expected to be the lowest in a cooling trend that should weaken by Thursday but linger through the weekend, forecasters said.

A low-pressure system centered in the mid-state area began moving south and cooled temperatures here slightly Saturday, replacing a high-pressure system that had encouraged unseasonable highs in the 80s at Lindbergh Field since Aug. 23.

The heat wave of above-average temperatures peaked Friday with a high of 90 degrees at Lindbergh Field--the top temperature for the month of August. By Labor Day, cooling was evident throughout the county, and the daytime temperature at the airport had dropped to 78 degrees. Tuesday’s high was 73.

Wide and abrupt swings from unseasonably warm to unseasonably cool temperatures have marked weather here since mid-summer. This week’s cooling trend mimics weaker low-pressure systems that forced temperatures below average for two periods in August.

Forecasters who had observed unseasonable weather throughout August were surprised to see the abnormal temperatures balance to produce a normal monthly average temperature. The sunshine count, however, was high.

With 79% of possible sunshine, the month tied as the fourth sunniest August on record. The all-time high was 84% in August, 1966.

Highs at the beach in the 60s today may inch up to the low 70s Thursday. South to southwest winds are expected to kick in gusts today at the seashore, Shigehara said.

Coastal strip highs aren’t expected to be above 73 degrees today or 75 degrees Thursday; nighttime lows should be in the 60s.

Inland highs that reached into the 100s on Friday are expected to be in the 70s today and Thursday. Lows will dip to between 57 and 64 degrees.

Mountain foothills, expected to be cool by day with highs in the 50s today and 58 to 64 degrees Thursday, may plunge to lows in the 30s. Winds in gusts up to 25 m.p.h. are expected in mountain and desert areas.

Desert skies will be partly cloudy with highs in the 80s today, and between 84 and 94 Thursday. Lows are expected to be between 65 and 75 degrees.