Hotter Than Summer, But Near Normal for Now

Now that summer is officially over in Southern California, it’s getting hot. Nothing strange about that.

“We stay warm in September,” said Stuart Seto, a meteorological specialist with the National Weather Service in Oxnard. “It happens almost every year.”

Uncomfortable as it was, Tuesday’s top reading of 90 degrees in downtown Los Angeles was still 17 degrees below the record for the date of 107, set in 1978. The normal high for the date is 82.

Farther inland, it was considerably hotter on Tuesday: 103 in San Bernardino, 102 in Hemet and Temecula, and 100 in Riverside.

The heat and low humidity hampered firefighters before they finally gained the upper hand against a stubborn, 200-acre blaze that burned one home and forced the evacuation of 20 others near Lytle Creek in western San Bernardino County.

Seto said the current spate of hot weather--expected to last through the weekend--is due in part to the maximum combination of solar angle and proximity to the sun that occurs near the autumnal equinox, which was on Saturday.

He said another major factor is the presence of weather patterns similar to those that trigger the warm, dry Santa Ana winds of October and November.

These patterns feature high-pressure systems over the Great Basin and Four Corners areas and low-pressure systems along the Pacific Coast. Air flows from high pressure to lower pressure, creating downslope winds that heat and dry out by compression as they sweep down coastal slopes toward the sea.

Because of local topography and the relative positions of the high- and low-pressure systems, these winds are primarily affecting Santa Barbara County right now.

Offshore winds below the unofficial Santa Ana minimum of 25 mph kept skies over most of Los Angeles, Orange, Riverside and San Bernardino counties clear, warm and dry on Tuesday.

Top temperatures included 101 at Pierce College in the San Fernando Valley, 98 in Chatsworth and Pasadena, 97 in Fullerton and Monrovia, 96 in Northridge, and 95 in Santa Ana. Forecasters said temperatures should be about the same today, dropping a few degrees, but remaining hot, through Monday.