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Why 2025 became the summer of flash flooding in America

The National Weather Service has already issued across the United States in 2025, and that as torrential downpours continue in late July. There's a good chance the U.S. will exceed its of around 4,000 flash flood warnings soon.

For communities in , , and , the floods have been deadly. And many more states have seen flash flood damage in recent weeks, including , , , and .

What's causing so much extreme rain and flooding?

I study along with the complex processes that lead to the devastating damage they cause.

Both the atmosphere and surface conditions play important roles in when and where flash floods occur and how destructive they become, and 2025 has seen some extremes, with large parts of the country east of the Rockies received at least from mid-April through mid-July.

Excess water vapor, weaker jet stream

Flash floods are caused by over short periods of time. When rain accumulates too fast for the local environment to absorb or reroute it, flooding ensues, and conditions can get dangerous fast.

During the warm season, intrusions of tropical air with excessive water vapor are common in the U.S., and they can result in intense downpours.

In addition, the —which move storm systems from west to east across the U.S.—tend to weaken during summer. As a result, the overall movement of thunderstorms and other precipitation-producing systems slows during the summer months, and storm systems can remain almost stationary over a location.

The combination of intense rainfall rates and extended precipitation increases the likelihood of flash flooding.

The surface rain falls on makes a difference, too

Local surface characteristics also play important roles in how flash floods develop and evolve.

When intense precipitation is combined with saturated soils, steep slopes, urban areas and sparse vegetation, runoff can quickly overwhelm local streams, rivers and drainage systems, leading to the .

Because the characteristics of the surface can vary significantly along a stream or river, the timing and location of a heavy downpour pose unique risks for each local area.

What's driving flash floods in 2025?

During the in Texas Hill Country on July 4, 2025, that killed , atmospheric water vapor in the region was at or . The storm hit at the headwaters of the Guadalupe River, over streams that converge in the river valley.

As thunderstorms developed and remained nearly stationary over the region, they were fueled by the excessive atmospheric water vapor. That led to high rainfall rates. Hours of heavy rainfall early that morning sent the river at a summer camp near Hunt, Texas, where more than two dozen girls and staff members died. Downstream at Kerrville, the river rose even faster, gaining .

Overall, a persistent atmospheric pattern in late spring and summer 2025 has included a and, along with lower atmospheric pressures, has supported excessive rainfall across the central and eastern U.S.

While the West Coast has experienced dry conditions in early summer 2025 due to a ridge of high pressure, the U.S. east of the Rockies has seen an with frontal boundaries and disturbances that produced thunderstorms and intense downpours across the region.

can also boost rainfall. The Caribbean and the Atlantic Ocean are for atmospheric water vapor in the central and eastern U.S. In summer 2025, that water vapor has created extremely humid conditions, which have produced very high rainfall rates when storms develop.

The result has been flash floods in several states producing catastrophic destruction and loss of life.

Looking to the future

The U.S. has seen devastating flash floods throughout its history, but rising global temperatures today are of flooding.

As ocean and air temperatures rise, atmospheric water vapor increases. Higher ocean temperatures can produce more atmospheric water vapor through evaporation, and a warmer atmosphere can hold more moisture, fueling downpours. In some high-risk areas, meteorologists, aware of the risks, say they are becoming about .

Currently, evidence shows in the overall global climate system as temperatures rise.