The U.S. Midwest will remain extremely hot and dry the next few days, adding more stress to crops already damaged by a summer heat wave, but some relief rains are expected over the weekend, forecasters said.
All-time high temperatures were forecast for many U.S. Midwest cities on Thursday. The midday temperature in Chicago was 99 F (37 C) and forecast to break 100. It was 100 F in Des Moines, Iowa, at midday and 97 in Columbus, Ohio.
The heat dome will hover over the Midwest until the weekend when temperatures were forecast to return to the mid 80s to the low 90s F, which is considered to be normal for this time of year, said Joel Widenor, a meteorologist for Commodity Weather Group, a U.S. advisory firm.
Some relief rains will accompany the drop in temperatures, he said.
But the midday weather updates for the Corn Belt called for the heat to return by the middle of next week.
"The end result is a little more threatening environment for the crops that are still struggling with dryness and heat issues," said Drew Lerner, a meteorologist and owner of World Weather in the Kansas City area.
The extreme heat and persistent dryness has become a huge worry for farmers and the grain trade, as the across the U.S. Midwest the corn crop is pollinating -- the key growth phase that determines yields. Iowa and Illinois alone produce a third of corn and soybeans in the United States, the world's top grower and exporter.
Drought conditions are the worst on corn and soybean crops since 1988, according to government data.
The U.S. drought monitor released on Thursday showed the drought intensifying across the central Midwest, with conditions deteriorating from Missouri to northern Wisconsin, eastward to Ohio.
Temperatures were likely to remain near or above 100 F on Friday. The heat stress on the crops will then dissipate as temperatures drop below 95 F.
There was little rain in the near-term forecast for key growing areas states such as Iowa and Illinois, but there were some showers expected in northwestern areas of the Corn Belt such as Minnesota, North Dakota and South Dakota.
"The general theme is going to be that really the hottest weather is in the very near term but the rains still will be slow to pick up here over the next couple of weeks," Widenor said.
Scattered rain fell in Minnesota, eastern Nebraska and northwest Iowa during the past two days.
By the weekend the showers, which could bring 1/4-inch to 1-1/4 inches of rain, were seen moving farther east into Wisconsin, Ohio and Michigan.
Crop fears have fueled CBOT's corn and soybean markets over the past two weeks. Corn prices hit a 10-month high of US$7.60 a bushel in the spot contract on Thursday. Soybeans touched a four-year top of US$16.44-1/2.
-- Mark Weinraub and Christine Stebbins write and report on grain markets for Reuters in Chicago.