Extreme precipitation events, as occurred in Europe in 2021, or western North America in 2023, with an intensity of 75 mm/day or 100 mm/day, respectively, exert a catastrophic impact. Lower-resolution (∼100 km) climate models cannot simulate the intensity or their response to greenhouse warming. Using a high-resolution (∼25 km) model capable of simulating such events, here, we show that the frequency-weighted area of such events over western Europe and the west coast of North America likely expands by more than 80% under approximately 4°C of global warming from historical levels. Along the west coasts of Europe and North America, the area impacted by atmospheric river-induced extreme precipitation events is projected to double, driven by intensified landfalling atmospheric rivers. Thermodynamic processes drive the increase, whereas dynamic processes reduce the intensity over western Europe but enhance it along the west coast of North America. Our findings provide policy-relevant information for climate adaptation strategies.