At least 81 people died in Texas flash floods, including several girls at a summer camp, after extreme rainfall caused the Guadalupe River and its tributaries to swell rapidly. The disaster, which occurred on Friday, is considered one of the worst flood events in the U.S. in the last 100 years. The water level rose approximately eight meters in just 45 minutes.

The Texas Hill Country, known as Flash Flood Alley, is particularly susceptible to flash floods due to its unique geology of steep cliffs and deep rivers, combined with warm and unstable air masses. Authorities did not issue an evacuation order before the floods, leaving many unprepared.

Texas faces the highest risk of flash floods in the United States, with Flash Flood Valley characterized by bare cliffs and dry, impermeable surfaces. Extreme rainfall quickly transforms peaceful rivers into dangerous torrents. Warmer air holds more moisture, exacerbating the risk of heavy rainfall, with air holding seven percent more water vapor for every degree of temperature increase.

The recent low-pressure system over central Texas was fueled by remnants of Tropical Storm Barry, absorbing warm, moist air from the Gulf of Mexico. While it is still too early to definitively link the rainfall to man-made global warming, the probability suggests a connection.

Evidence indicates that extreme downpours are increasing in Europe as well. Professor Jens Hesselbjerg Christensen notes that while Denmark is too small to be indicative, data from Germany and Sweden show a trend of intensifying downpours. The 2021 floods in Germany, which resulted in nearly 200 deaths, exemplified the danger of rapid-onset flash floods.

While Denmark is generally less at risk due to its flat terrain, cities like Vejle and Aarhus, with steep hills and central streams, could face amplified flooding during heavy rain. Vejle experienced flooding in September of last year due to persistent heavy rain. Despite perceptions that downpours have decreased since the 2011 Copenhagen floods, the professor stresses that downpours are localized and often miss major cities.

Record high temperatures in the Mediterranean can contribute to catastrophic rainfall in Northern Europe. Warm, humid air masses moving north from the Mediterranean can trigger extreme precipitation when they encounter cooler air.

Climate models predict that larger parts of Jutland could experience up to 50 percent more downpours by the end of the century. The capital region is projected to see a 30 percent increase in downpours under a scenario with medium-high CO₂ emissions and temperature increases, according to DMI’s climate atlas.