The bad? South Coast’s lowest-ever number of eight-hour ozone exceedances is still the worst in the country this year. The Valley’s lowest-ever is second worst. And third place is not even close to South Coast or the Valley.
Low pressure spinning off coast of California was the culprit on Monday.
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.”
Plan your picnic Friday, you live in Fresno. It’s a good bet you won’t see rain at Woodward Park or anyplace else in the city.
Since weather record-keeping began in the late 1870s, Fresno has never seen rain on June 21.
But that’s not the most interesting part of this trivia. According to the records, June 21 is the only rainless day of the year in Fresno.
In other words, all the torrid, parched days of July and August have seen at least some kind of rain in the last 130 years or so.
“Rain is pretty unusual in the summer for the San Joaquin Valley,” said meteorologist Paul Iniguez of the weather service in Hanford. “But we’ve recorded at least a trace on every day of the season in Fresno, except June 21.”
Iniguez said next month — July — is particularly dry in the Valley. He said there have only been three days since the 1870s when Fresno got more than .10 of an inch of rain. The amounts of rain were .14 of an inch in 1925, .22 in 1992 and .33 in 1913.
“The Valley has a very Mediterranean climate,” he said. “Summers are typically very dry.”
By the way, Friday is the first full day of summer. The solstice happens at 10:04 p.m. Thursday.