**2. Study Area and Data**

#### *2.1. Study Area*

This study was carried out in Iowa and Illinois, spanning across 52 counties (Figure 1), covering the region affected by the 2020 Derecho lodging disaster which occurred on 10 August 2020. Iowa and Illinois are located in the Western part of the Corn Belt region of the United States and are part of the top agriculture production states. Iowa has a total agricultural land of 30.6 million acres, accounting for 92% of the state's total land area while Illinois has a total agricultural land of 27 million acres, accounting for 75% of the state's total land area. The two-dominant crops in both states are corn and soybean. Other crops like wheat and winter wheat are also planted but they account for a very small portion of all the cropland. In this study, the estimation of lodging rate (lodged crop per unit area) was only focused on corn and soybean. In Iowa and Illinois, the climate is cold and temperate. In Iowa, the wettest month with the most precipitation is June with an average precipitation of 107 mm and an average temperature of 82 ◦F, while the driest month is January with an average precipitation of 23 mm of rainfall and an average temperature of 31 ◦F. In Illinois, the wettest month with the most precipitation is August in the Northern portion of Illinois with an average precipitation of 89 mm and

an average temperature of 82 ◦F, while the driest month is February with an average precipitation of 49 mm of rainfall and an average temperature of 35 ◦F.

**Figure 1.** Study area covering (**a**) the region affected by the 2020 Derecho lodging disaster in the states of Iowa and Illinois as shown by the red outline and (**b**) the 52 counties in the affected region.
