At least 40 people have been killed in the Plains and Midwest from a combination of tornadoes and flooding over a multi-day stretch of dangerous weather.

Floodwaters have started to recede in Missouri and Illinois, but the extensive damage left behind will require weeks or months to clean up. Missouri Gov. Jay Nixon said Tuesday that 7,100 homes and businesses were damaged or destroyed by the floods.

At least 29 people have lost their lives in the floods, and most of those deaths were caused by vehicles being swept away by swift-moving floodwaters.

(MORE: Latest News on the Deadly Floods)

Downstream, the Mississippi River has yet to crest along the Louisiana-Mississippi border, and residents have been warned that flooding could worsen in the coming days. Officials may be faced with the difficult decision of opening spillways to lessen the impacts of the flooding, but that would threaten hundreds of homes in the water's path.

Investigators from the National Weather Service said a tornado that hit Garland, Texas, Saturday was an EF4 – the second strongest tornado rating on the Enhanced Fujita Scale. The Garland tornado is only the second EF4 to hit Dallas County since 1950. In total, 11 people died in tornadoes that hit the Lone Star State on Saturday.

The twisters also left major damage in Blue Ridge and Copeville, among others. These tornadoes flipped vehicles off bridges, reduced homes to rubble and reportedly led to a large fire at a Sunnyvale trailer park that was mostly destroyed.