Monsoon storms swept into central Arizona on the evening of Aug. 14 and persisted into the early hours of Aug. 15, delivering heavy downpours, frequent lightning and strong winds across the Phoenix metropolitan area. The National Weather Service (NWS) in Phoenix reported localized rainfall totals exceeding half an inch and down-burst wind gusts of 40–50 mph as slow-moving cells trained over the city. Shortly after midnight, the agency issued a Flash Flood Warning for the north-northeast Valley after standing water up to two feet was observed along Interstate 17. An Areal Flood Warning later expanded coverage to parts of Maricopa and Pinal counties, with officials urging drivers to avoid low-water crossings and heed road closures. Scottsdale and Sun City West were among the communities recording more than half an inch of rain, while radar indicated additional convection blossoming over the wider metro area. The NWS said thunderstorms would remain possible through Friday, maintaining a 30 percent chance of further rainfall and localized flooding.