By Sam Nelson

CHICAGO (Reuters) - Small amounts of rain this week and early next week in about 70 to 75 percent of the U.S. Midwest crop belt will provide some relief to deteriorating corn or soybean crops from the relentless and spreading drought, meteorologists said on Monday.

"There's no huge change in the forecast today, maybe a little more favorable for crops but we couldn't have gotten much worse," John Dee, a meteorologist for Global Weather Monitoring, said.

Dee said a weather front would move into about 75 percent to 80 percent of the Midwest Tuesday through Thursday, leaving 0.20 inch to 0.60 inch of rain and a similar front was expected next Monday and Tuesday with about 70 percent coverage.

Temperatures will rise into the upper 90s (degrees Fahrenheit) to low 100s F early this week, cool to the 80s F by midweek then rise into the 90s F again by the weekend, Dee said.

"There are no sustainable soaking rains in sight. There is some slight relief but no huge reversal in the drought," Dee added.

Commodity Weather Group (CWG) on Monday said more than one-half of the Midwest would still be too dry and warm for at least the next two weeks and the most persistent heat was expected for the western Midwest.

"This will leave over one-half of the late-pollinating and filling corn and pod-setting soybeans subject to additional stress," CWG meteorologist Joel Widenor said.

CWG's Monday report said the drought was more focused on southern Wisconsin, western Illinois, southern and western Iowa, far northern and far western Missouri, southwest Minnesota, South Dakota, Nebraska and Kansas.

The devastating drought has been decimating corn and soybean crops in the southern Midwest and eastern Midwest in states such as Arkansas, Kentucky, Indiana, Ohio and southern Illinois.

Drought and heat in the United States led the U.S. Department of Agriculture last Wednesday to slash its corn production forecast to 12.970 billion bushels, down from its previous outlook for 14.790 billion and below the record crop of 13.1 billion bushels produced in 2009.

USDA last Monday dropped its estimate for U.S. corn good-to-excellent condition rating to 40 percent from the previous 48 percent. Traders expect USDA to show a similar decline in updated weekly crop progress data later on Monday, including a decline in soybean conditions.

A report from climate experts on Thursday said the Midwest was in the grips of the worst drought in a quarter of a century.

Nearly two-thirds of the nine-state Midwest region was in some stage of drought in the reporting week that ended July 10, up from just over 50 percent a week earlier, according to the Drought Monitor, a weekly report on drought throughout the country compiled by U.S. climate experts.

One-third of the region was in severe to exceptional drought, up from about a quarter of the region a week earlier, it said.

The worsening drought caused Chicago Board of Trade spot corn futures prices to soar nearly 45 percent in only six weeks with the price on Friday coming within a few cents of the record high of $7.99-3/4 per bushel hit 13 months ago.

Corn, soybean and wheat futures prices were sharply higher again on Monday as the drought continued to spread.

(Reporting By Sam Nelson; Editing by Maureen Bavdek)