Fresno spiked 110 degrees on Monday, the hottest day of the year. It broke a 121-year-old record and surprised a lot of folks who had seen forecasts of about 100.
What happened? It was sunnier than expected in the morning, and the San Joaquin Valley got a wind-blown taste of the southwest desert. Then the lightning and thunder show started in the evening.
The culprit was low pressure spinning in a counterclockwise direction in the Pacific Ocean, said meteorologist Paul Iniguez of the National Weather Service in Hanford.
“The counterclockwise spin brought a flow of air up from the desert,” he said. “It was hotter in the Valley than many desert locations. In eastern Kern County desert, the temperatures were in the 90s.”
Meteorologists call this kind of low pressure a “cutoff low,” because it is separated from the jet stream — the high elevation blast of wind coming across the Pacific eastward into the West Coast.
Without the jet stream to move it along, the low could sit in one place and spin winds into California.
The high temperature in Fresno was reported at 109, but it actually climbed to 110 after 5 p.m., Iniguez said.
The flow of air coming from the east continued into the evening and thunderstorms began to appear. There were power outages and fires. In Kern County, there were 1,600 lightning strikes, Iniguez said.
“There were probably more people who saw lightning than people who saw rain,” Iniguez said. “I wouldn’t call this weather unusual in August, but it’s not typical.”