The country’s vast population shift has left more people exposed to the risk of natural hazards and dangerous heat at a time when climate change is amplifying many weather extremes. A New York Times analysis shows the dynamic in new detail:

• Florida, which regularly gets raked by Atlantic hurricanes, gained millions of new residents between 2000 and 2023.

• Phoenix has been one of the country’s fastest-growing large cities for years. It’s also one of the hottest, registering 100 straight days with temperatures above 100 degrees Fahrenheit this year.

• The fire-prone foothills of California’s Sierra Nevada have seen an influx of people even as wildfires in the region become more frequent and severe.

• East Texas metro areas, like Houston, Austin and Dallas-Fort Worth, have ballooned in recent decades despite each being at high risk for multiple hazards, a fact brought into stark relief this year when Hurricane Beryl knocked out power in Houston during a heat wave.

“The more that people are moving into areas exposed to hazards,” said Jeffrey Schlegelmilch, director of the National Center for Disaster Preparedness at Columbia’s Climate School, “the more that these hazards can turn into disasters of larger and larger scale.”

In some places, population growth and development have already made disasters worse and more costly, leading to widespread damage and destruction, major stress on infrastructure and soaring losses for insurers and individuals alike. Yet studies show people continue to flock to many “hazard hotspots.”

Americans’ decisions about where to move are largely motivated by economic concerns and lifestyle preferences, experts said, rather than potential for catastrophe. Some move seeking better job prospects and a cheaper cost of living; others are lured by sunnier climates and scenic views.

“There are 20 different factors in weighing where people want to move,” said Mahalia Clark, a graduate fellow at the University of Vermont who has studied the links between natural hazards and migration in the United States. “Higher up on the list is where friends and family live, where I can afford to move. Much lower down is what is the risk of hurricane or wildfire.”

Widespread use of air conditioners has also supported Americans’ long-term southward shift, making places with hot summers but mild winters more attractive.

Yet even in booming southern metro areas, growth has not been evenly spread. Nor have departures from places like the Northeast. In many parts of the country, suburbs and exurbs have seen the biggest population gains in the last decade, while inner cities have often lost residents. The coronavirus pandemic turbocharged this trend.

This outward growth of population and development has increased many Americans’ exposure to natural hazards too, bringing more people into wildfire zones and giving tornadoes and hurricanes more chances to hit populated areas, a trend scientists call “the expanding bull’s-eye effect.”

To be sure, few places are completely safe. Much of Vermont, which is not highlighted as high risk in the maps above, saw devastating flooding last year following a record-breaking storm. But the Times’s maps focus on places with the highest risk, according to hazard data from CoreLogic, a property and risk analytics firm.

Other forces, including improvements to early warning technologies and stricter building codes, have helped reduce disaster risk and losses even as rapid population growth and development in high-hazard areas and climate change have increased the potential for harm.

“In a way, I see it as a race,” said Virginia Iglesias, a research scientist at the University of Colorado, Boulder’s Earth Lab. “We are trying to mitigate,” she said, even as hazards multiply and more people move into harm’s way, “increasing the probability of disaster.”

The Carolinas and Florida: More People in Hurricanes’ Path

Between 2000 and 2023, Florida added more than 3 million people through domestic migration. North and South Carolina added another 2.5 million.

Many of these new residents have settled in coastal communities that are at high risk for hurricanes. A storm-prone stretch of the Carolina coast that includes Myrtle Beach, S.C., has been a particularly popular destination for many retirees. So has much of Florida.

The influx of people into coastal areas with high hurricane risk — and the development that comes with a population boom — has increased the scope of disasters and the cost, studies show.

When Hurricane Ian hit the Cape-Coral-Fort Myers area in 2022, it killed nearly 150 people and caused more than $100 billion in damage, making it the third-costliest hurricane in U.S. history. Scientists found the storm bore the fingerprints of climate change, which most likely increased the amount of rain Ian delivered across Florida. But rapid population growth and development also changed the shape of the disaster.

In a detailed report published the following year, Swiss Re, a reinsurance company, found that the same storm would have been far less catastrophic — and expensive — if it had struck decades earlier. The biggest reason: Many more people, homes, businesses and other assets were now in the hurricane’s path.

While stricter building codes put in place by the state over the prior 30 years helped avert an even-worse disaster, the report found they were not enough. “Put simply,” Matt Junge, an analyst at Swiss Re, wrote in a blog post, “the benefits that Florida has reaped from strengthening its building codes over the last half-century have been overwhelmed by population growth.”

Some parts of Florida have lost residents in recent years: Surging housing prices have driven many locals from the Miami area, for example. But most of those leaving have resettled elsewhere in the state.

The Tampa Bay area has been one of the most popular destinations for people from across the country, despite facing a number of destructive hurricanes in recent years. Just last week, Hurricane Helene brought record-setting flooding to the region before tearing across the Southeast.

Repeat disasters have started to take a toll on many local residents. So has the soaring cost of home insurance in the state. High insurance prices have pushed some Florida homeowners to drop their coverage altogether. At the same time, several insurers have stopped offering new policies, citing mounting storm-related losses among other issues that have plagued Florida’s insurance market.

Insurers in other states, including parts of California and Texas, have also stopped offering home insurance policies or hiked premiums as losses from extreme weather events have increased.

Texas: Rapid Growth, Compounding Hazards

Metropolitan areas in East Texas have grown rapidly over the past two decades. The region has attracted millions of people from across the country, especially from more expensive cities in states like California and New York. Among the area’s attractions: a booming job market, especially for energy and tech workers, and cheaper housing compared to many coastal superstar cities.

At the same time, the region faces multiple extreme weather threats. Houston is regularly pummeled by hurricanes. Dallas-Fort Worth sits in an area at high risk for serious thunderstorms, hailstorms and tornadoes. Austin’s fringes have been pushing into more fire-prone territory. And each metro area is vulnerable to extreme summer heat.

Suburbs and exurbs have been the biggest magnets for domestic migration, drawing people from other states as well as nearby urban centers — a trend that accelerated across the country during the pandemic.

“We’ve seen these suburban ring and exurb areas just growing very rapidly,” said Lloyd Potter, Texas’ state demographer, noting that many businesses, especially new factories and data centers, have settled outside of city cores. Residents with families have also been drawn by the promise of “more space, good schools and affordable housing,” he said.

But rapid growth “creates a lot of challenges for these places too,” he added, including “a lot of demand for infrastructure; you need housing units, cars, roads, schools.”

The region’s breakneck growth and development have often worsened the impacts of natural hazards too.

When Hurricane Harvey, a slow-moving Category 4 storm, dumped more than four feet of rain on Houston in 2017, floodwaters displaced thousands, killed more than 30 and caused billions of dollars in damage. Several studies found that human-driven climate change intensified the storm’s torrential rains. But decades of sprawling urbanization also drove up Houston’s risk of flooding as absorbent wetlands were paved over and more homes were built in flood zones.

This summer, Hurricane Beryl ended in a different kind of disaster. As the destructive Category 1 storm swept across Houston, it ripped out trees by the root, felled power lines and caused more than two dozen deaths — many not from wind or flooding, but from what followed. The storm knocked out power for more than 2 million Houston residents, many of whom remained without electricity — and air conditioning — for weeks as temperatures soared. The situation became dangerous for vulnerable groups, especially the elderly: Houston-area hospitals reported a spike in heat-related illnesses, and Harris County’s medical examiner reported at least eight deaths from overheating.

CenterPoint, the region’s power provider, was intensely criticized for its response to the hurricane, with commentators pointing out that the company could have done more to prepare, including trimming trees and hardening more of the region’s electric infrastructure. Later reporting found that the utility had struggled to make necessary investments in system reliability while also working to accommodate population growth and respond to extreme weather.

The situation in the Houston region is a stark example of how expanding population and development can combine with rising hazard risk to severely strain critical infrastructure, said Michael Webber, a professor of mechanical engineering at the University of Texas at Austin.

“The geographic area is growing,” he said. “The number of meters is growing. The number of people is growing. The temperatures are increasing, so the peak demand for air conditioning is going up. And the industrial activity is growing.”

All of that is putting pressure on the power system, Dr. Webber said, adding: “It’s hard to expand and improve the system at the same time.”

California: Affordable Housing Crisis Meets Growing Wildfire Risk

Like many urban centers along California’s coast, San Francisco and the rest of the Bay Area saw large population losses in recent years. The region’s high housing costs have made it difficult for many people to stay, while the rise of remote work has allowed tech and information workers to live further away from their jobs.

Many former Bay Area residents left the state entirely, moving to cheaper metros in Texas, Idaho and other Western states. Others moved further inland in search of affordable housing and more space, often to California’s hot Central Valley or to the fire-prone foothills of the Sierra Nevada.

At the same time, wildfires have become more common and more powerful across the state, fueled by rising temperatures, drought and the long-term oversuppression of natural fire.

A 2022 study from the University of Wisconsin, Madison, and the U.S. Forest Service found that the two trends — more frequent, larger fires and the rapid growth of housing in flammable areas — have both contributed to the growing destructiveness of Western wildfires.

As people have moved deeper into wildfire zones, they have also increased the chance that fires will start in the first place.

“People bring ignitions with them,” said Dr. Iglesias, the climate scientist at the University of Colorado, Boulder, noting that a stray cigarette thrown out of a car window or a downed power line can each spark a devastating blaze. By moving into fire-prone areas, people “are not only putting themselves and their homes in harm’s way,” she said,“but they’re increasing the probability of fire too.”

To reduce risk, in 2008 California put in place a strict building code for high-risk areas designed to make new homes less likely to burn. Studies have shown that homes built to that code are more likely to survive when catastrophe strikes. But many older homes remain highly vulnerable to fire.

While some risk-reducing home upgrades are cheap and easy, said Emily Schlickman, an assistant professor of landscape architecture at the University of California, Davis, who studies wildfire risk to homes and landscapes, others can be a much bigger strain on budgets. “There’s low-hanging fruit,” she said, like putting metal mesh over vents to prevent embers from getting into the home. “But that’s very different from redoing your entire roof in metal,” she said.

Population growth and development in wildfire-prone areas have driven up other costs as well, including the price tag of firefighting services. A growing number of home insurers have now paused or stopped writing policies in California’s high-risk fire zones, pointing to growing wildfire-related losses, the impacts of inflation and state policies.

Although it’s too soon to say for certain, Dr. Schlickman said that the state’s insurance crisis has, anecdotally, been “a big eye-opener” for many residents.

“When you go to buy a house and can’t get a mortgage because of lack of insurance,” she said, disaster risk “goes from a No. 10 issue on your list to much higher.”