The effect of heat on grapes is dependent on many factors, including the way grapes are farmed. But buyers who “have been around a while” know that a prolonged stretch of very high temperatures in the growing areas “can contribute to having some issues later on,” said Kevin Beno, owner of Fresh Buyers Inspections Inc. in Visalia, CA, Aug. 8.

FBI is a quality-control company specializing in the on-ground inspection of grapes, tree fruit, citrus and melons out of California and southern Arizona. The company has been in business since 1991. The company’s customers are principally brokers, wholesalers and exporters.

“Whenever we see issues like this with weather,” Mr. Beno said, referring to an extended stretch of triple-digit temperatures during the first part of August, “customers want to be more informed of what is happening.” Consequently, “we tend to get a few more calls,” including “calls for certain orders where they might otherwise not call.”

When “everything is going well,” he said, some buyers will “just let things go. But when there have been weather extremes that could affect some of the grapes, “we will see more of a push for guys wanting their fruit looked at in more detail.”

That is “good for everybody,” he said. “It is good, obviously, for the receiver and the buyer, and it is good for the shipper, too. It helps them to have a set of eyes, too, on what they are shipping. They don’t want any headaches, either, especially when we get into the later part of the deal.”

Having been exposed to hot weather does not necessarily mean that the grapes will have problems. But there will be variations among labels and among lots, and that is why buyers often feel the need to use an inspection service such as FBI. They want to be sure that what is loaded on their truck is of a quality and condition that will meet their needs.

The varieties and the degree of maturity at the time of a heat wave affect susceptibility, but cultural factors do as well. Putting the right amount of water on the vines, for example, is important in keeping the grapes strong through a hot spell, and most growers “around here” are “real careful with the water,” Mr. Beno said. “They have been through this before.”

Having a good canopy in the vineyard is another important protection against the heat, shading the grape bunches and preventing sunburn, he explained.

Prolonged extreme heat can potentially weaken the shelf life of the harvested fruit, Mr. Beno said. Heat-stressed vines” will pull back and protect themselves … and the fruit kind of gets left behind.”

Each grower needs to make determinations as to how long each lot of grapes can be held and how far away it can be shipped, based on its condition. In most cases, “on the domestic side, if you pick, pack and ship,” the grapes are “going to be fine,” he said. But particularly for the later deal, if the fruit is being held for several weeks before shipment, “you might see a few issues here and there, on green grapes especially,” if grapes were put away that were not sufficiently strong.

Only the strongest grapes are considered suitable for export.

If growers “see some areas” in their vineyards “where they thing [the grapes] got hurt — either the fruit is weaker or they have some burn — they are going to tend to ... try to move it a little quicker” than grapes which are stronger and can hold on longer, he said.

California grape shipments will continue through the end of the year, with the later shipments having been held in storage for several weeks.

In general, “so far, quality has been very good” on the grapes from the San Joaquin Valley, Mr. Beno said. Sizing has been good, and “at this point,” condition is a little better than last year.

“Hopefully it will transition into the late deal on grapes,” he said.