Invisible Atmospheric Moisture Supercharges U.S. Summer Floods

An August 23 Washington Post analysis found atmospheric moisture running 5% to 15% above average across the Pacific and much of the United States this summer. The analysis linked extra moisture transported into the contiguous United States since June with record-breaking rainfall in parts of 44 of 48 states, covering about 90,000 square miles. NOAA separately reported that El Niño is strengthening, with more than a 90% chance of a very strong event during fall and winter 2026-27. NOAA also recorded eastern Pacific sea-surface temperature anomalies above 2 degrees Celsius in August. The moisture analysis used ECMWF atmospheric data and PRISM rainfall data. Scientists caution that abundant moisture raises the potential for extreme rainfall but does not guarantee flooding without weather systems capable of releasing it. The outlook for additional storms remains uncertain by location and timing. Seasonal forecasts indicate elevated precipitation risks in parts of southern United States.