The remnants of Hurricane Ida walloped the Northeast late Wednesday and early Thursday, delivering record rainfall in parts of New York and triggering flash flooding across multiple states. At least 14 fatalities were reported in New York, New Jersey and Pennsylvania, bringing the storms estimated death toll to 21.

Earlier, after Hurricane Ida smashed into the Louisiana coast as a catastrophic Category 4 storm, Gov. John Bel Edwards (D) warned that the death toll was likely to rise sharply as rescue crews scoured neighborhoods left in ruin. At that point, officials had confirmed just seven storm-related fatalities: three Louisiana residents, two electrical workers in Alabama and two people who died when floodwaters collapsed a highway in Mississippi.

But if previous record-breaking storms are any guide, Idas toll could climb further. Thats because even though evacuations and beefed-up coastal protections help spare lives as the storm rages, flooding, blocked roads and a blackout expected to last weeks threaten lives with waterborne illnesses, a lack of food and medicine, and no electricity to run vital medical equipment or keep insulin refrigerated. Those at risk are mostly poor people who couldnt afford the gas to leave or a hotel room to which they could flee.

Fatalities directly and indirectly tied to Hurricane Katrina, for example, are still a matter of public debate 16 years after the storm. Katrina hammered New Orleans and much of the Southeast in September 2005, and the estimated deaths slowly crept up , from 964 in early October 2005 to 1,306 in late November. The official tally currently stands at more than 1,800, according to federal statistics.

Hurricane Maria and Superstorm Sandy were similar stories. It wasnt until nearly a year after the 2017 hurricane ravaged Puerto Rico that the territorial government revised its official storm death toll from 64 to 2,975 in response to the findings of a government-commissioned study. A separate investigation by Harvard researchers concluded that more than 4,600 people died in the aftermath, primarily due to interruptions in medical care.

Sandy, which hit the Northeast in October 2012, left some of the poorest neighborhoods in the countrys richest metropolitan areas without power and inundated with water that, if it didnt destroy homes outright, later rendered them uninhabitable with toxic mold.