It’s far too early for a definitive estimate of the economic damage caused by Hurricane Harvey. Floodwaters still swamp large swaths of the Houston area and beyond, into far eastern Texas and Louisiana.

But three independent estimates from people who specialize in disaster and risk management show that the storm is likely to be the most expensive or second-most expensive natural disaster in the United States since 1980, the earliest year such comparable data was kept by the National Centers for Environmental Information. On Friday, estimates for Harvey from these groups ranged from $70 billion to $108 billion.

The estimates are unofficial and changing daily as the storm continues and as the scope of the damage is better understood. But even these initial estimates stand out on a chart comparing the costs of every natural disaster costing $1 billion or more since 1980 (adjusted for inflation).

Billion-dollar natural disasters since 1980 Circles are sized proportionally to their cost in 2017 dollars Winter storms, freezing Drought and wildfire Flooding Tropical cyclones Severe storms

Harvey’s toll may yet increase and put the storm on a scale of economic devastation with Hurricane Katrina, which the National Oceanic and Atmospheric Administration (NOAA) estimates cost about $160 billion in today’s dollars and resulted in 1,833 deaths.

There are several other estimates of the cost of Harvey not included here. A prominent one, by Joel Myers of Accuweather, is $190 billion. It is not included in the chart above because it may not be directly comparable with the estimates as NOAA calculates them. Mr. Myers’s estimate includes the “total negative impact on the economy,” he said, from supply chain interruptions to spoiled food.

“There are downstream impacts that other people might not have considered,” Mr. Myers said.

His prediction – nearly double the highest estimates included here – may ultimately prove to be correct. The estimates shown here have all been revised upward, though none show it to be more expensive than Katrina.

“Each day that passes, as the impacts multiply, it seems more likely that Harvey may ultimately eclipse the cost of Katrina, and it might not even be close,” said Adam Smith, a climatologist focusing on disaster economics with NOAA’s National Centers for Environmental Information. Mr. Smith has written about how NOAA estimates the costs of natural disasters.

The numbers for Harvey are educated guesses for now. It will be more than a month until NOAA releases its first official estimate, Mr. Smith said.

The groups making the estimates shown here are:

• RMS, a risk modeling firm based in California. It estimated the cost at $70 billion to $90 billion as of Thursday.

• Moody’s Analytics, a research firm. It estimated between $86 billion and $108 billion on Friday.

• Chuck Watson, a disaster modeler with Enki Research. He estimated $72 billion to $85 billion on Thursday.

Each of the three uses a mixture of models and observed data from the storm. They update their estimates as new information is available.

While no outside group can replicate the exact methodology that NOAA will use to assess the economic impact of the storm, Mr. Smith said the methods of these groups were broadly comparable to NOAA’s.

If anything, these numbers are likely to be conservative. Mr. Watson’s estimates for the cost of the storm have more than tripled, from his estimate of $22 billion on Aug. 25, the day before the storm made landfall. And Mr. Smith said even the first official account from NOAA, expected Oct. 6, is likely to be a lower-bound estimate, updated for months to come.

One reason estimates may continue to fluctuate is that flooding is an uncertain kind of damage to assess economically, in part because damage from floods is less likely to be covered by insurance. As the extent of flooding becomes better known, the uncertainty around these estimates will narrow.

Regardless, it’s clear this type of economic devastation from storms is becoming more common. In inflation-adjusted terms, the United States averaged fewer than three billion-dollar natural disasters per year from 1980 to 1990. Since 2010, it has averaged more than 10 per year.

Billion-Dollar Natural Disasters Since 1980 1980 1990 2000 2010 15 10 5 0 Billion-Dollar Natural Disasters Since 1980 1980 1990 2000 2010 15 10 5 0

Climate change is one reason for this: Global warming loads the atmosphere with more water vapor, which increases the potential for extreme rainfall events.