DC weather history for May 27: Catastrophic Ellicott City flooding for second time in less than two years

On this date in 2018, a catastrophic flash flood struck Ellicott City, Maryland, marking the town’s second devastating flash flood in two years, a reminder of its vulnerability to extreme rainfall events. The flood turned the city’s main street into a raging river, washing away cars and engulfing buildings with high water. In nearby Catonsville, Maryland, 13 inches of rain fell in three hours.

The event unfolded rapidly during the late afternoon and evening as thunderstorms repeatedly moved over the same area, a phenomenon known as “training.” Capital Weather Gang coverage described how these storms “unloaded torrential rain” over a narrow corridor, overwhelming the landscape and drainage systems. The National Weather Service issued a rare flash flood emergency, its most urgent warning, calling the situation “extremely dangerous and potentially catastrophic.”

The National Weather Service reported that more than 6.5 inches of rain fell in just three hours in Ellicott City.

As water surged downhill through Ellicott City’s steep terrain, historic Main Street, located in a valley where multiple streams converge, became a conduit for rushing floodwaters. Within minutes, water levels rose dramatically, trapping people, sweeping away vehicles, and forcing emergency crews into dozens of rescues. One person, a National Guard member attempting to help others, was killed in the flooding.

Meteorologically, the storm was fueled by an atmosphere loaded with moisture and a slow-moving front that allowed storms to repeatedly regenerate over the same location. The result was rainfall of extraordinary intensity — an event later classified as roughly a “1-in-1,000-year” occurrence.

The 2018 flood raised questions about changing rainfall extremes, urban development, and the town’s geography. Ellicott City’s setting makes it particularly prone to flash flooding when intense rain falls over a short period.

Here are articles on the event:

• Another catastrophic flash flood in Ellicott City — the second in two years
• Crews rescuing people as torrential floods hit Ellicott City
• The second 1,000-year rainstorm in two years engulfed Ellicott City. Here’s how it happened.
• ‘Are we going to die?’ a caller asks a 911 dispatcher amid Ellicott City flooding
• Ellicott City ‘hero’ urged friends to honor Memorial Day — then died trying to save a stranger
• Perspective: ‘Do you return?’ After another 1,000-year flood, Ellicott City’s shop owners need our help.
• ‘Beyond rescue’: Ellicott City’s bizarre, rainless flood and its deadly 20-foot wall of water
• Weather Service determines Sunday’s Ellicott City rainstorm was indeed ‘1 in 1,000’
• Event report, National Weather Service - Ellicott City & Catonsville, MD

Here are other notables from this day:

• Average high: 79
• Average low: 61
• Record high: 95 (1965)
• Record low: 42 (1915)
• Record rainfall: 1.50 inches (1885)