* Corn, soy ratings drop 2 points, will also fall next week
* Weather remains stressful for each crop
* Ratings for each worst since 1988 drought
* Conditions decline in top 4 corn, soy states (Updates with state-by-state details, background)
By Sam Nelson
CHICAGO, July 30 (Reuters) - Corn and soybean conditions in the U.S. Midwest deteriorated further last week as the most expansive drought in more than 50 years ate away at crop prospects in major producing states including Iowa and Illinois, government data on Monday showed.
The U.S. Department of Agriculture rated 24 percent of the U.S. corn crop in good-to-excellent condition as of Sunday and 29 percent of the soybean crop in good-to-excellent shape, both down 2 percentage points from the previous week.
The ratings for each were the worst since the comparable week in 1988, another year of severe drought in the nation's crop-growing mid-section.
Crops improved marginally in Ohio and Indiana where condition ratings were already among the poorest in the country and in smaller-producing states such as Wisconsin and Michigan, but those improvements were overshadowed by eroding ratings in the top producing states in the central and western Midwest.
Concerns that the most expansive U.S. drought since 1956 was intensifying in areas that had not been as severely impacted earlier in the season propelled U.S. corn and soybean prices to all-time highs this month.
Much of the U.S. corn crop was largely beyond repair, but soybeans were moving into their critical flowering and pod-setting phase of development when heat and moisture stress can be devastating to yields.
In Iowa, Illinois, Nebraska and Minnesota, the top 4 corn and soybean producing states, corn crop ratings fell by 2 to 5 points and soybean ratings dropped 3 to 4 points.
A Reuters poll of 10 analysts had expected a 3 percentage point drop in the corn rating and a 2 point drop in soybeans. Graphic on corn: r.reuters.com/muj29s Graphic on soybean: r.reuters.com/nuj29s ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^>
The U.S. corn crop was rated 41 percentage points below the five-year average and 5 points above the 19 percent good-to-excellent rating in the comparable week during the drought of 1988.
The soybean rating was 34 points below the five-year average and 10 points above the same week in 1988.
Analysts and crop experts also said further declines in condition ratings could be expected next week as weather remained stressful to each crop.
Dry and hot weather in the U.S. Midwest for the next week or two will further erode crop conditions, trimming this year's corn and soybean production, an agricultural meteorologist forecast on Monday.
"It looks like a continued trend of below-average precipitation in the Midwest for the next week to 10 days," said John Dee, meteorologist for Global Weather Monitoring.
Temperatures this week will warm into the upper 80s to low 90s degrees Fahrenheit (30-35 degrees Celsius), with only a few light showers in the east on Monday and some rainfall later in the week, he said.
"There are no widespread soaking rains in sight. Thursday and Friday there could be scattered showers, and by the weekend from 0.30 to 0.80 inch (0.8-2 cm) with coverage of about 75 to 80 percent," Dee said.
"There won't be as much stress as recently, but crops will continue to deteriorate," Dee said.
Analysts have rapidly been lowering their outlooks for this year's corn and soybean crops, boosting the price of each to record highs. (Reporting by Sam Nelson and Karl Plume; Editing by Dale Hudson and Marguerita Choy)