Hurricane Ida generated a tornado outbreak as it traversed the Southeastern, Mid-Atlantic, and Northeastern United States. Thirty-six confirmed tornadoes touched down from Mississippi to Massachusetts; one person was killed in Upper Dublin Township, Pennsylvania, and several people were injured in Alabama, New Jersey, and Pennsylvania. The most active and destructive part of the outbreak occurred during the afternoon of September 1, when several strong tornadoes struck Maryland, New Jersey, and Pennsylvania, including an EF3 tornado which impacted Mullica Hill, New Jersey. The same storm later dropped an EF1 tornado that prompted a tornado emergency for Burlington, New Jersey and Croydon, and Bristol, Pennsylvania, the first of its kind in the Northeast, as well as the first such alert associated with a tropical cyclone or its remnants. This outbreak severely impacted New Jersey and the Philadelphia Metropolitan Area, a region which had been significantly impacted by strong tornadoes from another outbreak that occurred just over a month prior, as well as several weak tornadoes from the remnants of Tropical Storm Fred two weeks earlier. Overall, the 36 tornadoes killed one person and injured seven others.

Meteorological synopsis

At 16:55 UTC on August 29, Hurricane Ida made landfall near Port Fourchon, Louisiana, with sustained winds of and a central pressure of . Strong low-level shear, daytime boundary heating, and weak inland buoyancy led to an increasing risk for tornadoes across the Southeastern United States. The Storm Prediction Center (SPC) issued a slight risk for severe weather for the Central Gulf Coast for three straight days between August 29-31. Numerous weak tornadoes touched down in Mississippi, Louisiana, and Alabama during this time. One EF1 tornado caused considerable damage in Saraland, Alabama on August 30, injuring three people. A small slight risk was also issued in the Mid-Atlantic for the Southern Delmarva Peninsula on August 31, where a confluence zone was expected to have an increasing westerly mid-level flow in response to Ida, although it was not the only influence in this area. Two weak tornadoes occurred in Southwest Virginia that afternoon.

As Ida became extratropical and moved into the Northeastern United States on September 1, a strengthening low-level jet (LLJ) along and south of a warm front coupled with a very moist atmosphere and sufficient surface heating led to a more substantial risk for tornadoes between Washington, D.C., and New York City and the SPC issued a tornado-driven enhanced risk for severe weather for this region. This included a 10% tornado risk with a 30% damaging wind risk added later on. That afternoon, several supercells formed across the D.C. metropolitan area and quickly became tornadic as they moved northeast. An EF2 tornado struck Annapolis, Maryland, causing significant structural and tree damage throughout the city. Another EF2 tornado caused severe damage in a residential neighborhood in Oxford, Pennsylvania. Later, a large EF2 tornado struck Upper Dublin Township, Pennsylvania, severely damaging buildings, homes, and trees, killing one person and causing a few minor injuries. An intense EF3 wedge tornado destroyed several homes and a dairy farm in Mullica Hill, New Jersey as well, injuring two people. An EF1 tornado produced by the same storm prompted the issuance of the first ever tornado emergency the Northeast, as well as the first such alert associated with a tropical cyclone. A few other weak tornadoes also touched down later that evening and into September 2 before the remnants of Ida moved offshore, ending the outbreak.

Confirmed tornadoes

August 29 event + List of confirmed tornadoes – Sunday, August 29, 2021EF#LocationCounty / ParishStateStart Coord.Time (UTC)Path lengthMax width EF1WSW of Pass Christian to SW of DiamondheadHarrison, HancockMS11:23–11:28A waterspout moved onshore from the Gulf of Mexico damaging several homes, with one sustaining extensive roof damage. It continued to damage homes as it tracked northwest into the Bay of St. Louis. The tornado tracked near Diamondhead as it moved onshore from the bay. Shingles were removed from the roof of a nursing center as the tornado crossed I-10 before dissipating shortly thereafter. Trees were snapped or uprooted along the path as well. EF0GulfportHarrisonMS22:15–22:19Numerous trees and tree limbs were downed, including one large tree that was uprooted onto two houses. A house, a strip mall, and another building sustained roof damage as well. EF1Eden Isle (1st tornado)St. TammanyLA23:33–23:38Two buildings at a condominium complex had their roofs partially torn off. Numerous houses were damaged and trees were downed. EF0SE to NW of PearlingtonHancockMS23:59–00:09A waterspout moved onshore, blowing down road signs and posts. Trees and roofs of homes were damaged. EF0Eden Isle (2nd tornado)St. TammanyLA01:56–01:57A brief tornado damage roofs and fences and uprooted trees. EF0ESE of Waveland to Shoreline ParkHancockMS03:11–03:14A waterspout moved onshore and caused minor damage to the roofs of several homes and an apartment complex. Several trees were also snapped or uprooted. EF0NE of Waveland to NE of Shoreline ParkHancockMS03:15–03:18A waterspout moved onshore, where the roofs of several homes sustained minor damage. Several trees were snapped or uprooted as well. EF0Henderson PointHarrisonMS03:37–03:38A waterspout formed over the Mississippi Sound and moved inland. Several homes and a detached garage were damaged, trees were snapped or uprooted, and power lines were snapped.

August 30 event + List of confirmed tornadoes – Monday, August 30, 2021EF#LocationCounty / ParishStateStart Coord.Time (UTC)Path lengthMax width EF0Biloxi (1st tornado)HarrisonMS09:18–09:19A very brief tornado caused minor damage to several homes and several apartment buildings. EF0Biloxi (2nd tornado)HarrisonMS10:55–10:56A brief tornado inflicted minor damage to several homes and a small office complex. Large tree limbs were snapped. EF0NW of Mississippi CityHarrisonMS12:44–12:45A brief tornado damaged the roofs of several homes and snapped numerous trees. EF0E of Gulfport to WSW of BiloxiHarrisonMS12:49–12:51Trees were snapped and uprooted at a golf club. Several homes sustained damage, and a warehouse lost some of its roof panels. EF0Biloxi (3rd tornado)HarrisonMS12:50–12:55Trees were downed and several houses sustained roof damage. The tornado crossed Big Lake and caused minor damage more homes. EF0Biloxi (4th tornado)HarrisonMS12:56–12:58Several homes sustained minor roof damage. Portions of roofing were torn off at a bank and a restaurant, and trees and fences were damaged along the tornado's path. EF0Pascagoula to SE of HelenaJacksonMS14:37–14:57A waterspout moved ashore, causing light damage to multiple homes. Tree limbs were damaged. EF1Saraland to E of BucksMobile, BaldwinAL17:20–17:43The roof of a motel was partially removed just west of US 43 in Saraland, and several sections of another motel's roof were removed. The roof of an industrial building was partially removed and an 18-wheeler was overturned. Trees were uprooted or snapped along the path, including some that fell onto a home near I-65. Three people were injured. In November 2023, this tornado was reanalyzed and had its path length adjusted from to due to a narrow swath of uprooted and snapped trees noted on Planet and Worldview satellite imagery. The ending point was also extended further to the northeast into the Mobile River delta. EF1E of MalcolmClarke, BaldwinAL18:05–18:10In November 2023, a new tornado was found along the Alabama River based on a narrow swath of tree damage noted on Planet and Worldview satellite imagery. EF1ESE of Rockville to WSW of AlmaClarkeAL18:25–18:28A mobile home was rolled and another home lost much of its roof. Trees were snapped or uprooted as the tornado tracked through a heavily wooded area. EF0SE of TroyPikeAL19:02–19:09A few trees were downed or had limbs snapped off. EF0SE of TuskegeeMaconAL20:45–20:46Trees and tree limbs were blown down, and a home sustained siding damage.

August 31 event + List of confirmed tornadoes – Tuesday, August 31, 2021EF#LocationCounty / ParishStateStart Coord.Time (UTC)Path lengthMax width EF0SW of Peterman to Jones CrossroadsHoustonAL20:59–21:08Trees were downed onto a mobile home. Farther along the path, the doors and siding of a warehouse were damaged and the roof of a shed was peeled off. EF1SE of RadfordMontgomeryVA22:34–22:38A barn was damaged and several trees were snapped or uprooted. EF1NW of MerrimacMontgomeryVA22:59–23:00Several trees were uprooted and snapped, and a swing was destroyed. EF0Midland CityDaleAL23:14–23:17Bleachers and a dugout at the Dale City High School were damaged. Numerous homes in Midland City sustained minor roof damage, and trampolines were lofted into the air. Several trees were also blown down, some of which fell onto and damaged a home. EF0N of Bailey CrossroadGeneva, HoustonAL23:34–23:40This tornado moved through open fields before damaging a barn near the end of its path.

September 1 event