Slow-moving thunderstorms drop historic rainfall, causing catastrophic flooding in parts of Connecticut

Slow-moving thunderstorms produced extremely heavy rainfall in parts of southwestern Connecticut on August 18, 2024, particularly affecting Fairfield and New Haven counties. The historic downpour caused widespread flash flooding, with Monroe experiencing a rare one in a 200-year event.

Southwestern Connecticut was hit by exceptionally heavy rainfall on Sunday, August 18, with some areas recording up to 300 mm (12 inches) and prompting the National Weather Service (NWS) to issue a Flash Flood Emergency.

The most affected regions included Fairfield and New Haven counties, where the deluge caused significant flash flooding, leading to multiple water rescues and substantial damage to infrastructure.

David Stark of the NWS office in New York reported that parts of southwestern Connecticut received between 152 and 254 mm (6 – 10 inches) of rainfall within a six to nine-hour period, with the majority of the rain falling during the afternoon. Monroe in Fairfield County was hit particularly hard, recording 254 mm (9.98 inches) of rain. This volume of rainfall was classified as a one in 200-year event for the city.

The NWS office in New York issued a Flash Flood Emergency for several communities in southwestern Connecticut, describing the situation as “particularly dangerous” and noting that “widespread water rescues are taking place” as rainfall rates reached between 25 and 51 mm (1 – 2 inches) per hour. The heavy rainfall overwhelmed drainage systems, leading to severe flash flooding that washed out roads and stranded vehicles in cities such as Stamford, Danbury, and Southbury.

Flooding was also reported in cities such as Oxford — where an astonishing 342.9 mm (13.5 inches) were reported through 23:00 LT on Sunday, Seymour, and Cheshire.

In Danbury, emergency services responded to a mudslide at the Woodland Hills Complex on Shelter Rock Road, which caused a gas leak and led to evacuations. The NWS and Danbury Emergency Management coordinated the response efforts as utility crews worked to secure the area.

In neighboring New Jersey, flash flooding led to the delay of Amtrak trains between New York and Philadelphia on Sunday evening. The severe weather also disrupted air travel, with over 700 flights canceled across the three major airports near New York City—JFK, Newark, and LaGuardia. The Federal Aviation Administration (FAA) implemented ground stops at these airports, which remained in effect until late Sunday evening.

As the rain subsided, the NWS continued to monitor the situation, with Flash Flood Warnings extending into northeast New Jersey and southeast New York through Sunday night.

According to the NWC, there is a Slight Risk of excessive rainfall over parts of New England on Monday, August 1.

“A front extending from the Northeast Coast across the Mid-Atlantic/Southeast Coast and then across the Gulf Coast State will move off most of the Eastern Seaboard while lingering over the Southeast by Wednesday [August 21],” NWS forecaster Ziegenfelder said.

“The boundary will produce showers and thunderstorms with heavy rain over parts of New England as a plume of moisture feds into the area. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of New England through Tuesday morning [August 20].

The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas the most vulnerable.

Moreover, showers and thunderstorms will develop along the front from the Mid-Atlantic to the Southeast and the Gulf Coast State. Showers and thunderstorms will also develop over parts of the Central Appalachians and Ohio Valley on Monday.

Updates

15:55 UTC, August 19

According to Oxford Fire Department Chief, Scott Pelletier, two people were found deceased in the town of Oxford following severe flooding. The news comes after officials reported one missing person in the town, so it’s still not clear whether that person is among the two confirmed dead.

References:

¹ Water rescues underway in Connecticut after flash flooding causes mudslides, washes out roads – FOX Weather – August 18, 2024

² Short Range Forecast Discussion – NWS/WPC – Issued at 03:43 EDT on August 19, 2024

³ 2 killed and about 100 evacuated by rescue crews as flash flooding hit parts of Connecticut and New York – CNN – August 19, 2024

Teo Blašković

I'm a dedicated researcher, journalist, and editor at The Watchers. With over 20 years of experience in the media industry, I specialize in hard science news, focusing on extreme weather, seismic and volcanic activity, space weather, and astronomy, including near-Earth objects and planetary defense strategies. You can reach me at teo /at/ watchers.news.

• Teo Blašković

  G3 – Strong Geomagnetic Storm Watch issued for June 4 and 5 following three significant solar flares
• Teo Blašković

  X1.0 solar flare erupts from geoeffective Region 4455
• Teo Blašković

  M9.3 and M7.7 solar flares erupt from AR 4455, launching Earth-directed CMEs
• Teo Blašković

  Kīlauea sets lava-fountaining record with episode 48, Hawaii