East of the Cascades, fruit growers are scrambling to get ready for a heat wave that could bring a peak temperature Tuesday of 113 degrees in Yakima and hang around until at least Friday, when a high of 107 is forecast.

Such an extreme surge in temperatures would complicate the already difficult job of picking for a cherry harvest now in full swing. To help workers escape the worst of the heat, some growers are preparing for predawn harvests while others plan to have crews start at sunrise and quit earlier in the day.

A prolonged spell of over 100 degrees also could damage some crops.

Farmers have experienced intense heat for days on end later in the summer. But the forecast heat, arriving so early in the growing season, would be a first, and makes it harder to predict what will happen.

“We are traveling in absolutely uncharted waters next week,” said B.J. Thurlby, president of the Northwest Cherry Growers. “We just don’t know what this is going to do.”

The heat wave arrives as some 10 million pounds of fruit a day are being picked from orchards in Washington and other Northwest states by tens of thousands of workers. The quality of the fruit has been good, and market demand has been strong, according to Thurlby.


The weather forecast has raised concerns that cherries at the top of some trees could shrivel, a condition that makes them unmarketable. And in areas where cherries are not yet ripe, high temperatures could cause the fruit to temporarily stop cell division, and that could prevent them from reaching full size.

“Plants are like people. They like warm weather, but if they get too hot, they slow down,” said Jon DeVaney, president of the Washington State Tree Fruit Association.

The start of the harvest for apples, the state’s top-grossing crop, is still weeks away. But the heat could cause some apples to get unsightly blotches from “sunburn,” and not make it to market.

“The closer to market, the more acute the damage,” said Sean Gilbert, president of Gilbert Orchards in the Yakima Valley. “We’re still a ways away from harvest so that is not as big a concern.”

In recent years, some farmers have started putting shade cloth over their apples. It’s an expensive undertaking, so Gilbert has only used it on some of his highest value apples, including 50 acres of Honeycrisp that just got a canopy completed this past week as the heat wave approached.

The heat wave is forecast to absorb a broad swath of irrigated farm country in Eastern Washington. In Othello, a prime potato-growing region, high temperatures are forecast by the National Weather Service to reach 112 on Tuesday.


Researchers have found that potato growth shuts down above 95 degrees. So, a week of 100-plus degrees in early summer could slow growth and stress plants, said Dale Lathim, executive director of the Potato Growers of Washington.

The heat can also cause some tubers to end up with hollow heart or another condition that turns their ends from starch to sugar.

“It is safe to say there will be some impact. Right now, I’m just very concerned but not alarmed,” Lathim said.