By Karl Plume

(Reuters) – A harsh drought grew more severe across major parts of the U.S. farm belt this week, threatening recently planted corn, soybean and spring wheat crops in Iowa, Minnesota and the Dakotas, meteorologists and climatologists said on Thursday.

Rains forecast for the northern Midwest and Great Plains this weekend and next week will bring relief to some areas. But the severe moisture deficits suggest crop yields in key U.S. production areas remain at risk.

Drought has already scorched much of the U.S. West, prompting farmers in California to leave fields fallow and triggering water and energy rationing in several states.

Crop development in the central U.S. is highly watched this year as grain and oilseed prices hover around the highest in a nearly a decade and global supplies tighten.

“It’s certainly causing some stress there, especially to the spring wheat,” said Don Keeney, senior agricultural meteorologist with Maxar Technologies.

About 41% of Iowa, the nation’s top corn producer and No. 2 soybean state, was under severe drought as of Tuesday, up from less than 10% a week earlier, according to the weekly U.S. drought monitor published on Thursday.

Cooler weather this weekend and some rain through next week will bring some relief to crops in the western Corn Belt, although far northern areas may see less rain.

“Montana, Nebraska, Minnesota and even northern Iowa would still be a little shortchanged, especially the Dakotas,” Keeney said.

Conditions in North Dakota, the top producer of high-protein spring wheat that is used in bread and pizza dough, remained dire, with about two-thirds of the state under extreme or exceptional drought, the most severe categories.

October to April was the driest stretch in North Dakota history since record keeping began 127 years ago, Gov. Doug Burgum told a town hall meeting in Washburn, North Dakota, on Wednesday.

“We know that we’ve got a full-blown crisis in the state,” Burgum told the meeting.

More than 100,000 acres, or 156 square miles, of North Dakota have already burned in wildfires this year, up from about 12,000 for the entire fire season last year, Burgum said.

Farmer and North Dakota Grain Growers Association Director Cale Neshem called the heat and dryness a “double whammy” that will slash his wheat harvest.

“There’s not going to be much there,” he said.

Drought in the western Corn Belt has already likely trimmed the U.S. corn yield average by 2 to 4 bushels per acre, said Dan Basse, president of AgResource Co in Chicago.

However, conditions in July and August, critical months for corn and soybeans, respectively, will determine the extent of yield losses and the price response, he said.

Grain and soybean futures on the Chicago Board of Trade fell sharply on Thursday as rain in the near-term forecast triggered risk-off selling.

“If we don’t get the rain, it’s going to be something to behold on the upside (for prices) because the yields will fall off the table,” Basse said.

(Reporting by Karl Plume, Tom Polansek and Julie Ingwersen in Chicago; editing by Jonathan Oatis)