Valley’s heat wave scorches fruit, lowers milk production

One more day above 100: A respite from temperatures of more than 100 degrees is promised beginning Saturday, according to the National Weather Service, but residents of the central San Joaquin Valley can expect one more day of the hot weather Friday.

The high today is expected to reach 101 degrees with a low tonight of 70. That should make Saturday’s expected temperature of 96 degrees seem pleasant. The thermometer is expected to keep dropping through the weekend, with temperatures in the low 90s by Tuesday.

The weather service attributes the change to monsoon moisture moving into the central and southern Sierra Nevada and nearby deserts. There may also be thunderstorms in the Sierra.

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People and pets aren’t the only ones withering under triple-digit temperatures.

The heat wave that on Thursday brought a fifth consecutive day of 100 degree-plus temperatures to Fresno is taking its toll on Valley agriculture and air quality.

Farmworkers stop harvesting by early afternoon, sluggish cows produce less milk and fruit trees and vines go into survival mode.

“Trees and plants just seem to shut down when it gets this hot,” said Kevin Day, a tree fruit adviser with the University of California Cooperative Extension in Tulare County. “And the fruit just doesn’t ripen.”

Long stretches of extreme heat can also cause dark-skinned fruit, such as plums, to sunburn or sustain internal damage.

“The fruit on the tops of the trees just gets cooked,” said Mike Naylor, a Dinuba tree fruit farmer. “But right now, I am more concerned about my guys than the fruit.”

On extremely hot days, Naylor starts his crews at 5:30 a.m. so they can finish picking by early afternoon. On Thursday, when the temperature was forecast to hit 106 — the high was actually 108, one degree shy of the record for the date, set in 2002 — Naylor’s workers were done picking by 1:30 p.m.

“When we hit these temperatures, you really have to stay on top of things,” Naylor said.

Grape growers face a similar battle against long stretches of extreme heat as hot temperatures stifle a vineyard’s development.

“Instead of producing sugar and enlarging the berries, the vines just maintain,” said Stephen Vasquez, a UC grape adviser.

Vineyards without a large canopy of leaves expose tender immature grapes to the sun, causing them to become sun damaged.

How much damage the heat has caused Valley agriculture remains to be seen, industry officials said.

On Valley dairies, extreme heat is hard on the cows, so farmers opt for mechanical solutions more often used to cool down people.

Tulare County dairy farmer Rob Fletcher uses fans and water misters in his barns to lower the temperature by at least 15 degrees. Fletcher said that while cows can tolerate the Valley heat, they generally produce less milk during the summer months.

“They can handle a few days over 100 degrees,” Fletcher said. “But when you have longer periods of 100-degree days and humidity, that is what really hurts.”

Dairies were particularly hard hit in 2006, when 14 straight days of 100-degree temperatures contributed to the deaths of more than 30,000 cows statewide.

Pet owners need to be careful about how quickly temperatures can rise inside their vehicles.

The Central California Society for Prevention of Cruelty to Animals reported several calls Thursday of pets left in vehicles, spokeswoman Beth Caffrey said.

“When the heat goes up, the calls go up quickly,” Caffrey said. “One person was golfing. One was at a doctor’s office. One was out to eat.”

It is a crime in California to leave an animal unattended in a vehicle where its health could be endangered. Violators could be fined or sent to jail, according to the state Penal Code.

Along with punishing pets, crops and livestock, the high heat also contributed to the Valley’s deteriorating air quality. On Thursday the Valley violated the federal eight-hour ozone standard for the sixth day in a row. The problem is expected to continue today with has a forecast high of 102.

Fresno County’s pollution forecast on Thursday was among the five worst in the country, according to the U.S. Environmental Protection Agency. Clovis violated the federal standard by midday.

Ozone, which can trigger asthma attacks and other lung problems, is created when sunlight and heat cook pollution gases from cars, diesel trucks and dairies. The Valley has some of the worst ozone problems in the country.

National Weather Service meteorologist Jim Bentzien said that despite the recent string of 100-degree days, it isn’t a record breaker.

That happened in July 1985 when triple-digit temperatures baked the Valley for 20 straight days.

The Valley also experienced 19 straight days of 100 degree-plus days in 1966, 1981 and 2005.

And if the forecast holds, Fresno will reach eight straight days of triple-digit temperatures on Sunday. Bentzien said Monday’s high is expected to reach 98, an average temperature for this time of year.

Next week, the temperature is expected to drop down between the mid- to upper 90s.

By Robert Rodriguez