Tornado outbreak sequence of August 4–8, 2023

From August 4–8, 2023, several active days of severe weather impacted the United States, where numerous tornadoes struck the Eastern United States, the Plains, and the Midwest. An EF3 tornado formed in Lewis County, New York, causing significant damage to homes, barns, a ski resort, and a motel. Another EF3 tornado touched down near Yuma, Colorado, causing significant damage to several structures in Yuma County, and a second tornado formed afterwards. In Baring, Missouri, a strong EF2 tornado struck the downtown area, damaging homes and injuring two people. Another EF2 tornado touched down in both Sangamon and Christian counties in Illinois, resulting in extensive tree damage along its path. The third EF2 tornado of the outbreak struck western portions of Knoxville, Tennessee, damaging multiple buildings including an apartment complex. This severe weather outbreak left approximately 1 million residents without power and led to over 1,000 preliminary wind reports. Additionally, heavy rainfall prompted a rare flash flood emergency in Cambridge, Maryland. Two non-tornadic fatalities (one in South Carolina and the other in Alabama) occurred as well.

Meteorological synopsis
A moist and unstable air mass and very strong winds aloft were present on August 7, with a shortwave trough progressing towards northern portions of Appalachia, and convective available potential energy in the 2500-3500 values yielded for severe thunderstorm development. Thermodynamic and kinematic energy in and east of central portions of the Appalachian Mountains also contributed to thunderstorm development. A level 4/moderate risk for severe weather, along with a 10 percent tornado risk, a significant 45 percent wind risk, and a 15 percent hail risk was issued by the Storm Prediction Center on August 7, including the Washington, D.C. metro area, the first moderate risk in decades for the DC area. Several severe thunderstorms formed ahead of a cold front in eastern Ohio, eastern Kentucky and West Virginia and later congealed into a quasi-linear convective system while approaching Washington D.C., Philadelphia, and Charlotte, North Carolina, bringing widespread damaging winds.

Non-tornadic impacts
Over 1,000 preliminary wind reports were recorded as severe weather impacted the East Coast of the United States on August 7. This led to widespread transit and Amtrak train delays in both the Northeast megalopolis, Great Lakes and Southeastern United States.

A Major League Baseball game between the Washington Nationals and the Philadelphia Phillies at Nationals Park was postponed on August 7 due to the inclement weather. The baseball game between the New York Mets and Chicago Cubs saw a 2-hour and 9 minute delay due to the rain at Citi Field. A Carly Rae Jepsen concert at The Rooftop at Pier 17 in New York City was cancelled due to a lightning storm. A 2023 Leagues Cup match between the Philadelphia Union and New York Red Bulls was postponed by a day. Several state governors, including Maryland governor Wes Moore, New York governor Kathy Hochul, and West Virginia governor Jim Justice urged people to stay alert, and to be prepared. Hochul's administration and local officials in New York were on stand-by for clean-up and response efforts, while Justice declared a State of Preparedness for all counties in West Virginia. Schools in Tennessee and Georgia were closed. Tornado watches and warnings were posted across ten states from Tennessee to New York, covering 29.5 million people. U.S. government offices in Washington, D.C. were closed early in anticipation of severe weather. Joe Biden's trip to the western United States was delayed 90 minutes.

A rare flash flood emergency was issued for Cambridge, Maryland, where flood damage and water rescues occurred as 4 in of rain fell in two hours. Power lines fell in Westminster, Maryland, including on MD 140, trapping more than forty people in their cars after live power lines fell behind and in front of vehicles. Montgomery Parks closed Sligo Creek Parkway and a road because of the threat for flooding, and damaging winds, causing trees to fall. A U.S. District Court sentencing was postponed due to severe weather, and tolls on I-66 reached nearly thirty dollars. Extra trains were operated by the Washington Metro to assist in people to get to their residences, and the Emergency Operations Center was activated. Train stations also operated an extra hour because Beyoncé's tour paid $100,000 to do so for fans to arrive at FedExField in Landover, Maryland, and to help people get home. FedexField was also under a "shelter in place" order due to the imminent severe weather threat, and it was lifted nearly two hours later. Despite the severe weather, a Pink concert was allowed to proceed, but inclement weather forced fans at Nationals Park to remain at the concourse.

Fallen trees trapped hikers and campers at Fall Creek Falls State Park, and forced the park to close. Damage occurred in eastern Kentucky and western North Carolina. Flooding occurred in numerous towns in Massachusetts, including North Andover, Lowell, and Needham. The Knoxville Utilities Board in Knoxville, Tennessee, stated that the damage across eastern Tennessee was "widespread and extensive".

On August 8, addition flash flooding resulted in the Maine Turnpike reducing their speed limit to below 45 mph south of Falmouth. In Syracuse, New York, record rain of 2.45 in poured down, which resulted in lengthy closures on I-81 and I-690 throughout the day on August 8. More than nine airports issued ground stops, including LaGuardia Airport, Ronald Reagan Washington National Airport, Hartsfield–Jackson Atlanta International Airport, and Baltimore/Washington International Airport. More than 1,700 flights were cancelled and nearly 9,000 were delayed across eastern United States airports impacted by severe weather. At least one million power outages occurred across the eastern United States, and two people were killed.

On August 8, the storms in Colorado produced a 5.25 in hailstone in Kirk that became the largest hailstone in state history in terms of diameter.

The American Red Cross were prepared to respond if conditions were necessary.