The Mississippi River, swollen by another round of downpours Monday, hit record flood levels at some Iowa towns Tuesday and threatened to keep rising.
Officials warned that miles of earthen levees already are in danger of collapse, and storms were forecast through the end of the week in the flood-weary region.
Evacuations were taking place in small communities in Missouri, Illinois and Iowa as the muddy river expanded.
Weeks of heavy rains have pushed the upper Mississippi and its tributaries far out of their normal channels, replacing livestock and crops with fish and silt and flooding hundreds of homes.
Many levees "are really taking a hit. They are quite stressed. There is water nearly to the top. They're saturated. Boils are developing," and it is likely "that some will fail," said Ron Fournier of the Army Corps of Engineers' Rock Island, Ill., office.
Near Peruque, Mo., rising water Monday broke through a levee four miles from the Mississippi's normal channel.
The earthen embankments protect thousands of acres of cropland and small farm towns on both sides of the river. Many larger cities are generally safer because they have built concrete and stone flood walls.
Experts believe that from 3 million to 3.8 million acres of soybeans remain unplanted in the Midwest because of drenched and flooded fields, some far from the river.
Rainfall of two inches or more was common in hot-weather thunderstorms breaking out across parts of Iowa, Illinois, Wisconsin, Minnesota and eastern South Dakota. Up to five inches of rain fell in portions of Iowa, said Jim Candor, a meteorologist with Accu Weather Inc.
Downstream from Davenport, the river hit a record 22.5 feet Tuesday at Burlington, Iowa, and was expected to climb another foot by Friday. It also hit a record 23.8 feet at Keokuk, Iowa, with an additional 2.7 feet expected by Friday.
In the southwest corner of Missouri, far from the Mississippi, three people drowned Tuesday when a flash flood swept two vehicles off a bridge over Flat Creek, near Cassville. Several other drowning deaths have occurred on the Mississippi and tributaries in the last two weeks.
The rainfall across the watershed has been phenomenal.
Weather Services Corp., a private forecaster, said Des Moines got 21.29 inches of rain in the last 30 days--622% of normal, and Minneapolis had 12.61 inches--371% of normal.
All commercial and recreational traffic remained indefinitely tied up on a 436-mile stretch from East Dubuque, Ill., at the southern edge of Wisconsin, to near Lock and Dam No. 26 north of St. Louis.