For the second straight summer, San Luis Obispo County is experiencing cooler-than-normal weather.
Local weather expert John Lindsey said Monday that daily high temperatures for July across San Luis Obispo County were below historical averages, mirroring what took place in 2010.
In San Luis Obispo, the high last month averaged 75.1 degrees. The historical average for the month in the city is 78.3 degrees.
In Paso Robles, the high last month averaged 89.7 degrees — well below the historical average of 93.8, said Lindsey, a communications specialist at PG&E and longtime Central Coast weather forecaster.
The cooler temperatures gave rise to an unusual sight at the California Mid-State Fair’s rodeo Saturday night — widespread use of sweatshirts and jackets to take the chill off the evening show, during which temperatures dropped into the 60s and there was a steady breeze.
The cause of the cool weather?
“A persistent trough of low pressure along the West Coast produced below-normal temperatures in San Luis Obispo County for the month,” Lindsey said.
The low pressure allowed winds to blow in from the cold Pacific Ocean and cool down the county.
This year follows the summer of 2010, which was also cooler than normal. In his analysis, Lindsey looked at average temperatures — including both daytime highs and overnight lows — and found that Paso Robles and San Luis Obispo have been cooler the past two Julys from the historical average.
“It’s unusual to see a trough of low pressure setting off the West Coast for two consecutive years,” Lindsey said.
He reviewed records going back two decades and did not find any other consecutive summers of below-normal temperatures.
The forecast for this week shows cooler-than-normal conditions continuing, Lindsey said. Today will be warm, with the high in San Luis Obispo near 80 and Paso Robles reaching more than 95 degrees. But coastal valleys and the North County will experience cooling Thursday and into the weekend. By Friday, Paso Robles will have a high of 88, and San Luis Obispo will warm to just 72 degrees.
“It will probably be early next week when temperatures may begin to warm back up to near normal with night and morning low clouds along the coast,” Lindsey said. “There is no sign of any extreme heat over the next seven to 10 days or longer.”
Local weather stands in sharp contrast to summer so far in the Midwest and East, Lindsey noted. More than 2,500 high temperature records were set last month for cities east of the Rocky Mountains.
Lindsey said Washington, D.C., averaged 84.5 degrees — its hottest July on record. Dallas recorded 30 straight days of highs above 100-plus degrees.