It was mid-July and already this summer he had become a leading contender for hottest in recorded Texas history. In San Antonio, which by July would normally have about three days of triple-digit heat, there were three dozen. Houston, Waco and Austin also saw temperatures 5 to 8 degrees above normal. The state is baking, and Texans have been using record amounts of electricity to stay cool.
New calculations suggest that, by the middle of this century, this record-breaking summer in Texas may seem normal.
Across much of the United States, millions of people are expected to experience extreme temperatures more often and for longer periods of time—a threat that will increase as climate change worsens. The new data, released Monday by the nonprofit First Street Foundation, calculates the heat risk faced by every property in the contiguous United States over the next 30 years, the life of a typical mortgage, providing some of the most detailed estimates nationwide. It uses heat index, a measure of how hot it feels outside, including temperature and humidity.
A Washington Post analysis of the group's data found that current climate conditions have forced 46 percent of Americans to endure at least three consecutive days of heat above 100 degrees, on average, each year. Within the next 30 years, this will increase to 63 percent of the population.
Nowhere is the risk more widespread than in the South, where global warming is expected to produce an average of 20 additional days of triple-digit heat per year. In some southern states like Texas and Florida, residents could see more than 70 straight days with the heat index exceeding 100 degrees Fahrenheit.
“We're talking about taking the summer, which is already hot, and extending it for months,” said Jaime González, director of the Houston Healthy Cities program for the Nature Conservancy of Texas. “This will cause all kinds of disruptions to everyday life.”
That data comes as more Americans are moving to some of the hottest parts of the United States. For more than a decade, census data has shown that Sun Belt states like Arizona, Texas and Florida are attracting new residents, while states in the Northeast and Midwest are not.
The larger pattern identified by First Street's model suggests that people living in the South are likely to experience some of the most dramatic changes in the coming decades. An earlier analysis found that the southern half of the country also faces the greatest fire risk.
First Street's analysis of property-level heat exposure is based on a combination of high-resolution measurements of surface temperature data, tree cover, impervious surfaces — such as pavement and asphalt — and proximity to water. It incorporates global climate models from the United Nations Intergovernmental Panel on Climate Change and is based on a moderate scenario in which global greenhouse gas emissions peak around 2040 and then decline slowly. If countries act faster or fail to enact climate-friendly policies, the outcome may change.
Areas with at least three
consecutive days of
dangerously hot
Percent of the population
living in exposed areas
dangerously hot
Ariz., Colo., Idaho,
Mont., Nev., NM,
Utah, Wyo.
Del., Fla., Ga., Md.,
NC, SC, Va., W.Va.
Iowa, Kan., Minn.,
Mo., ND, Neb.,
SD
Ill., Ind., Mich.,
Ohio, Wis.
Conn., Mass.,
Maine, NH,
RI, Vt.
Areas with at least three in a row
days of dangerously hot
The percentage of the population living in
areas exposed to dangerously hot
Ariz., Colo., Idaho, Nev.,
Mont., NM, Utah, Wyo.
Del., Fla., Ga., Md.,
NC, SC, Va., W.Va.
Iowa, Kan., Minn., Mo.,
ND, Neb., SD
Ill., Ind., Mich.,
Ohio, Wis.
Conn., Mass., Maine,
NH, RI, Vt.
Areas with at least
three consecutive days from
dangerously hot
The percentage of the population living in
areas exposed to dangerously hot
Ariz., Colo., Idaho, Mont.,
Nev., NM, Utah, Wyo.
Del., Fla., Ga., Md., NC,
SC, Va., W.Va.
Iowa, Kan., Minn., Mo.,
ND, Neb., SD
Ill., Ind., Mich., Ohio, Wis.
Conn., Mass., Maine,
NH, RI, Vt.
The analysis found that Miami-Dade County in Florida would likely undergo the most extreme change. While the county sees about 50 heat index days above 100 degrees, it is likely to have 91 baking days by 2053.
“We know we have a heat problem here. That's right in line with what we expect,” said Jane Gilbert, Miami-Dade's director of heat.
Unlike the West and Midwest, which have been scorched by extreme heat waves this year, South Florida has been chronically exposed to high heat for months, Gilbert said. This increases energy costs and puts outdoor workers, the homeless and those who cannot afford to air-condition their homes all day at risk. The county has designated May 1 through Oct. 31 as the official heat season and has launched an awareness campaign targeting neighborhoods with the highest heat hospitalization rates.
[Why summer in America is becoming longer, hotter and more dangerous]
Gilbert said having heat screens at the property level could help county officials advocate for more tree planting and painted roofs that reduce the need for air conditioning.
“If it's really good modeling, it's extremely valuable in helping us develop policies that require cooling,” he said.
Florida tops the states that will see the biggest increase in heat index days over 100 degrees. However, residents along the Gulf Coast and Southeast Atlantic are also expected to experience more weeks of dangerous heat due to poor summer conditions, low elevation and warm Gulf of Mexico waters.
Even hotter temperatures are expected to hit a section of the country stretching from northern Texas and Louisiana to Illinois and Indiana. While the central United States isn't typically seen as bearing the brunt of the summer heat, First Street's analysis found that tens of millions more people living in that region are likely to see a heat index above 125 degrees by mid century. The team calls this region the “extreme heat zone.”
Located between the Appalachian and Rocky Mountains, this region of the country “forms almost a bowl that funnels moisture into the region, which raises those 'sensible' temperatures,” said Jeremy Porter, chief researcher at First Street.
By mid-century, the number of regions experiencing at least one 125° heat index day will increase from 50 to more than 1,000.
Days with extreme
dangerous heat in 2053
Heat Index ≥125°F
By mid-century, the number of regions experiencing at least one 125° heat index day will increase from 50 to more than 1,000.
Days with extreme
dangerously hot in 2053
Heat Index ≥125°F
By mid-century, the number of regions experiencing at least one 125° heat index day will increase from 50 to more than 1,000.
Days with extreme
dangerously hot in 2053
Heat Index ≥125°F
By mid-century, the number of regions experiencing at least one 125° heat index day will increase from 50 to more than 1,000.
Days with extremely
dangerously hot in 2053
Heat Index ≥125°F
According to the National Weather Service, at a heat index of 125 degrees — which the agency classifies as an “extreme danger” day — heat stroke becomes “very likely.” And although there is no fixed temperature limit at which roadsbridges and trains begin to fail or water pipes break, recent examples show that it doesn't take a 125-degree day to overtax basic infrastructure.
[What extreme heat does to the human body]
Uneven risk
Heat is the top weather related killer in the United States. But like other impacts of climate change, it is felt unevenly. The poor, the elderly, very young children and people with certain chronic conditions are most at risk.
The city's treeless neighborhoods, filled with buildings, parking lots and paved roads, absorb and retain more heat than areas with tree-lined streets and parks. Scientists call this the urban heat island phenomenon. Nationally, this pattern is unfolding in city after city, concentrating the heat on low-income majority Black and Latino neighborhoods designated as risky investments decades ago.
Today, about 64 percent of all Black people in the US are experiencing a dangerous heat wave, defined as more than three consecutive days with a heat index above 100 degrees. But that will rise to 79 percent in 30 years, making a population already more vulnerable to heat significantly more exposed.
Percentage of population affected
with dangerously hotby race
Percentage of population affected by
dangerously hotby race
Percentage of population affected by dangerously hotby race
The Post also found that by the middle of this century, 71 percent of the nation's poorest neighborhoods will likely experience extreme heat.
Excessive heat will also make the work more dangerous. Today, there are about 3.8 million people who work outdoors and experience at least one severe heat wave. In 30 years, that number will increase by nearly 30 percent to 4.9 million.
In Houston's Gulfton neighborhood, a shift to more days of dangerous temperatures and humidity will expose the area's 45,000 residents — many of them recent immigrants from Afghanistan, Syria and Central America — to unbearable levels of heat. The neighborhood has a park and few trees. Two years ago, when Houston officials worked with scientists and volunteers to map the heat island phenomenon, they discovered parts of Gulfton were 17 degrees warmer in the afternoon than the coolest neighborhood measured.
González said that until recently, discussions about climate change in Houston have been dominated by discussions of flooding and sea level rise. The devastation unleashed by Hurricane Harvey in 2017 forced the city to grapple with the possibility of more storms. Now, record-setting summer heat is forcing another shift in focus, he said.
“We're getting a small preview of what it could look like if we don't take more action,” González said.