Fruit growers in the U.S. Pacific Northwest are worried about the impacts of the heatwave that is expected to bring a peak temperature of 113°F (45°C) in Yakima and hang around until at least Friday, when a high of 107°F (42°C)  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, The Seatle Times reports.

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,” B.J. Thurlby, president of the Northwest Cherry Growers, was quoted as saying. “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,” Sean Gilbert, president of Gilbert Orchards in the Yakima Valley, was quoted as saying. “We’re still a ways away from harvest so that is not as big a concern.”