Hot Winds Blow-Dry Region, Sweep Pollution From Skies

It’s not quite fast or widespread enough to be considered a traditional Santa Ana, but a northeastern wind that has created a high pressure dome over Southern California can be thanked for the sudden summer-like burst of sun and heat.

Indeed, temperatures have blazed in Ventura County’s valleys throughout the week.

On Wednesday, Simi Valley hit a record 101 degrees, the hottest day on this date in 21 years. Temperatures reached 104 in Thousand Oaks and 102 in Ojai, but meteorologists with the National Weather Service could not say if either was a record.

Along the coast in Ventura, temperatures hit 87 degrees, not a record but considerably warmer than the 69-degree high the day before.

Because the wind was moving only about 15 mph through the valleys, and 25 mph to 30 mph in the mountains, it took a couple of days longer to push back a thick marine layer and sea breeze that had conspired to yield a Seattle-like gray chill along the coast.

The northeastern condition--viewed as a sunny reprieve or an oppressive heat wave depending on where you live--is nearly over, experts say.

By Friday, the wind should turn and the coast return to its cooler state, said Stuart Seto, a weather specialist at the National Weather Service in Oxnard.

By Saturday night or early Sunday, low clouds and fog are expected to reach area valleys, Seto said. That could cool much of the east county, as well as neighboring Los Angeles County, where temperatures in several locations were inching toward record-breaking marks around 100.

The coast’s cool gray weather that has prevailed for much of September is caused by a combination of a thick layer of marine air and cooler ocean water, caused by La Nina, which in turn cools the sea breezes passing above it.

The next northeast wind could be faster and hotter. The Santa Ana season--which brings hot dry winds of at least 35 mph through the mountains and 25 mph through the valleys--typically begins in October and lasts through early spring.

Meanwhile, the heat and gusty winds offer some advantages. The intense heat shatters warm-air inversion layers that trap pollutants, and winds sweep soot and ozone away.

The result is more clean air for the county, which is on a record-setting pace with one month remaining in the ozone season, said Kent Field, meteorologist for the Ventura County Air Pollution Control District.

Ozone barely tipped the moderate scales in the east county on Wednesday, while clean air prevailed over the coasts. Even Simi Valley, Ventura County’s smog hot spot, experienced stellar visibility, with vistas stretching 43 miles in the late afternoon, Field said.

Staff writer Gary Polakovic contributed to this report.