Two key ingredients cause extreme storms with destructive flooding – why these downpours are happening more often

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Shuang-Ye Wu, University of Dayton

(THE CONVERSATION) A powerful storm system that stalled over states from Texas to Ohio for several days in early April 2025 wreaked havoc across the region, with deadly tornadoes, mudslides and flooding as rivers rose. More than a foot of rain fell in several areas.

As a climate scientist who studies the water cycle, I often get questions about how extreme storms like these form and what climate change has to do with it. There’s a recipe for extreme storms, with two key ingredients.

Recipe for a storm

The essential conditions for storms to form with heavy downpours are moisture and atmospheric instability.

First, in order for a storm to develop, the air needs to contain enough moisture. That moisture comes from water evaporating off oceans, lakes and land, and from trees and other plants.

The amount of moisture the air can hold depends on its temperature. The higher the temperature, the more moisture air can hold, and the greater potential for heavy downpours. This is because at higher temperatures water molecules have more kinetic energy and therefore are more likely to exist in the vapor phase. The maximum amount of moisture...