Temperatures to surpass 100 degrees during weekend heatwave

The mass of hot, humid air that produced oppressive weather earlier this week in New England, the Midwest and the Rockies was flowing into Southern California on Thursday, where it will generate the first major heat wave of summer in one of the driest regions of the country.

The heat wave will peak on Friday when temperatures reach117 in Ocotillo Wells, 114 in Anza Borrego State Park, 113 in Valley Center, 111 in Santee and Ramona, 109 in Campo, 105 in Escondido, 99 in Julian and 87 on Coronado, according to the National Weather Service.

“Thursday will be warmer than (Wednesday), but (Friday is when) it’s going to get really hot,” said Jimmy Taeger, a weather service forecaster.

Forecasters aren’t planning to issue a fire weather alert. Although temperatures will be high, the winds will be weak and the humidity will be in the acceptable range.

Still, SDG&E and local fire authorities will be monitoring wildland areas, where the vegetation has already withered. San Diego International Airport has only received 3.32 inches of rain since October 1st — a figure that’s nearly 7 inches below average.

During the same period a year ago, the airport had recorded almost 13 inches. Federal forecasters say it’s unlikely that the county will get significant rain before late October or early November.

The lack of rain has made firefighters wary of the type of wildfires that have erupted recently in Northern California.

The outbreaks include the County Fire in Yolo and Napa counties. Within a matter of days, the blaze charred more than 82,000 acres of land. Firefighters were working Thursday to bring the fire under control.

A distant change in the weather might help San Diego County get through the weekend ahead without suffering its own wildfires.

Earlier this week, Tropical Storm Fabio roared to life off the west coast of Mexico and briefly entered the so-called “Southern California swell window.” That’s an area offshore where a storm can direct wave energy into Southern California.

Fabio did whip up energy that will arrive in San Diego County on Thursday and Friday in the form of long-shore currents. The currents — which run roughly parallel to shore — pose a threat to swimmers and surfers. Fabio is also producing rip currents, which are equally dangerous.

But forecasters say Fabio did not send warm, unstable air toward San Diego County, where it could have produced thunderstorms whose lightning can start wildfires. As of late Wednesday Fabio’s moisture stream was headed for the southwestern U.S., where it will have little affect on California’s weather.

Such problems probably raised little or no interest Wednesday in Del Mar, where the San Diego County Fair concluded the 2018 season.

Visitors thronged throughout the Del Mar Fairgrounds under spotless blue skies, which slowed foot traffic from the barns to the midway to the outlying rides to the ferris wheel.

At several, the air temperature rose, which could have made things miserable. But then the wind picked up, racing across the coolish-ocean to the shore.

Most people call it the sea breeze. Forecasters have a different term: “Nature’s A.C. system.”

Union-Tribune reporter Bradley J. Fikes contributed to this report.

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