The $325 Thompson price puts pressure on the packers to raise the price significantly higher than last year’s $1,700 per ton.

Not all Thompson growers have the options of green or dry, since many vineyards are old and will not tolerate mechanical harvesting.

Hand-harvesting is expensive and there is a looming labor shortage. It takes 40 to 45 people per acre to hand-harvest green grapes for drying into raisins on paper trays.

“We have been talking to the tree fruit people, and they are saying they have to make do with fewer people,” said Goto.

(For more, see: Labor shortage looms over wine grape harvest)

It takes 20,000 to 30,000 people to hand harvest the Central San Joaquin Valley green crop for raisins. “We are talking to labor contractors, and they are saying they anticipate having the workforce to harvest and roll the crop.” How quickly that can be done is another question.

It once required up to 50,000 workers during a six-week period to harvest the valley’s raisin crop. This has been reduced with 30 percent to 40 percent of the valley’s raisins now mechanically harvested. Even then, it takes about 20 people per acre to do all the field work associated with mechanical harvest like cutting canes ahead of the grape harvesters and picking up the dried raisins.

The labor shortage is not unexpected. There have been reports of labor shortages in cherries, strawberries and vegetables all year long, says DiBuduo. “This could be a major factor in a grower’s decision to go to the winery or make raisins.”

DiBuduo says 95 percent of the valley’s wine grapes are machine harvested, but still contract harvesters are having difficulty hiring skilled laborers to operate the harvesters and other equipment used for mechanical harvesting.

Weather could play a significant role in the final wine and raisin tonnage. As fall approaches, growers typically worry about rain and cold weather. This year, it is excessive heat.

It was hot around the July 4 holiday weekend, when temps reached 108 F and above in the valley. It slowed down sugaring, but did not sunburn fruit, says DiBuduo.

By mid-August, however, another heat wave hit and temperatures soared to 111 F on Saturday, Aug. 11 in Fresno. The weather forecast called for temperatures to hold at 100 degrees or above for at least a week. “We could see damage from this heat,” he says.

Although raisin harvest is still a couple of weeks away, excessive heat and a short labor supply could cause problems there, according to Goto. A prolonged heat wave could dry the grapes into raisins quickly and if not turned and rolled quickly, there could be damage.