File:Flooding on the Mississippi River in Illinois and Iowa (MODIS).jpg

English: May 3, 2023 April 18, 2023

A winter filled with record-breaking snowfall followed by spring storms and rising temperatures triggered heaving flooding along the Mississippi River in late April and early May 2023. According to the Minnesota Department of Natural Resources, the winter of 2022-2023 was one of the snowiest on record across most of Minnesota. As of April 20, 2023, Duluth measured 139 inches of snow over the winter, setting a new all-time record as it surpassed the previous 135.4 top snow. St. Cloud’s winter was its second snowiest winter since record-keeping in the state began 100 years ago, with 86.6 inches.

The built-up snow, which is called snowpack, is beneficial as it holds water that, if released slowly, can help keep growing conditions excellent through the heat of summer. But, when a “big melt” occurs and the snow turns to water all at once, damaging floods can follow. As melting snow and spring downpours cause rivers to rise along the Mississippi River and its tributaries, starting from the north and flowing southward, residents are filling sandbags and trying to protect their property.

This year’s springtime floods reached major level in Minnesota, Illinois, and Iowa by late April or early May, with rising waters continuing southward along the Mississippi. As of May 6, the National Weather Service advised that the Mississippi River had crested in most cities in Minnesota by April 28, and most of the crests fell within the top 5 crests on record. Major level flooding occurred at Wabasha, Winona, Trempealeau, La Cross and McGregor. It will take until around May 10 for most sites in that state to fall below Flood Stage, and another week after that for the river to return to its banks. As of May 6, the Mississippi River had crested in most locations in Illinois and Iowa, with moderate flooding remaining in from Dubuque to Camanche, Iowa and major flooding between Le Claire and Burlington, Iowa and minor flooding in the more southerly town of Keokuk.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired two false-color images of the springtime flood in Iowa and Illinois, one on May 6 and the other on April 18. This type of false-color image helps differentiate water, which appears blue, from bright green vegetation. Sparsely vegetated or open land appears tan. Each image can be viewed by clicking on the dates.

The Mississippi River flows through the center of the image, and is heavily flooded. In the north, the Rock River flows westward into the Mississippi at South Rock Island, Illinois with Davenport, Iowa across the Mississippi. The water appears higher in the Rock River and other nearby rivers on April 18. The town of New Boston, Illinois sits near where the Iowa River meets the Mississippi, located just southwest of center in this image. What appears to be a bulge in the Mississippi just north of the Iowa River is Lake Odessa, and Port Lousia National Wildlife Refuge. This more southerly location is more heavily flooded in the May 6 image, as the large islands in Lake Odessa can be seen on April 18 but are submerged in the later image.