Thermal index, description: This is how to measure heat waves
Heat waves are becoming more frequent worldwide. But how do you measure heat waves? I’ll explain it.
USA TODAY
The cooling system in her two-storey apartment in Albuquerque, New Mexico has always been unreliable. However, last summer it failed for several weeks and the heat became unbearable. Erin Ashlock Romero packs his bags, grabs three children, including a 1 year old, and moves into his mother’s one-bedroom apartment to escape the high temperatures.
She said many families were in the building, but not everyone was that lucky.
“You can imagine it being very difficult for people who couldn’t go anywhere else,” Ashlock Romero said.
Albuquerque is one of the hottest places in the country and over time it got hotter. In 2024, the thermal index calculated by factoring temperature and humidity exceeded 90 degrees in 77 days from the 66th day in 2023 and the 52nd day in 2022.
Similar trends disrupt everyday life in communities across the nation. 2024 is the hottest year of record, and scientists hope this trend continues.
Spring 2025 has already become one of the hottest records for the neighboring United States, USA Today reports. According to the National Oceanic and Atmospheric Administration, at least 99% of the chances this year are the top five global temperatures.
USA Today analysis of Heat Index data for 310 major cities since 1985 found that most of them (approximately 8/10) had an increase in each year’s days with a heat index of 90 degrees or higher.
The most sharp increase was seen in the south, southwest and southeastern cities, but only the North Rockies and the Plains and upper Midwest had declined.
What’s even worse is that most cities have long stripes on hot days of over 90, hitting the first 90-degree day of the year, watching the last day.
Last year, Ashlock-Romero said he started to feel very hot in May and still felt that way in October. “We really didn’t have many breaks,” she said.
Heat depends on both temperature and humidity. As these rise, the body struggles to cool itself by sweating, increasing the risk of heat-related illnesses. The heat index combines both factors to measure how these conditions affect our body.
National Weather Service classifies Feat Index levels from “caution” from 80°F to “extreme danger” above 125°F.
Long-term exposure to a heat index above 80 degrees can lead to fatigue, and the risk continues to increase as it heats up. Elderly people, children, and outdoor workers are generally at a higher risk of fever-related incidents.
Fever is a leading cause of weather-related deaths in the country, according to the Centers for Disease Control and Prevention. Previous reports also show that the likelihood of an accident increases as temperatures rise.
In 2022, when she became pregnant with her third child, Ashlock Romero said that sometimes she died from extreme heat.
“Being at home and trying to do anything was impossible because I had gone through those episodes and even been out for a long time,” Ashlock Romero said. “I’ve had a lot of situations, or I like the fainting spell, and it was exacerbated by the heat.”
Between school shooting and rising temperatures
Whitney Holland loved calling himself an HVAC expert when he was a third-grade teacher at a public school in Los Alamos, New Mexico. Monica was stuck thanks to her crafty tricks on the classroom thermostat.
Her district’s cooling system triggers the trigger at 75 degrees, but at Pinon Elementary School, the 36-year-old found a way to spike in temperature readings and activate the cooling system.
“Wet paper towels will not be made until a certain threshold set by the district is reached,” Holland said.
In her decade as a teacher, the Netherlands learned safety protocols for school shootings, but the rise in fever has created a different kind of challenge for her and her teachers across the country. The Netherlands said the cooling infrastructure in many schools is outdated and upgrades are needed to keep up with the changing climate.
Since 2021, as president of the American Federation of Teachers’ Federations, the Netherlands has asked state authorities to fund these upgrades.
“As public school teachers, we teach all these safety protocols about shootings. We lock the doors and keep them closed, and the windows closed,” Holland said. “But we’re also fighting these rising temperatures.”
Last summer, schools in Rio Rancho also frequently experienced extreme heat, but they had to delay the start date of the semester to keep students safe from swelling temperatures.
Another place
Born and raised in New Mexico, Nathaniel Matthews Trigg lived in Seattle during the unprecedented heat wave of 2021 and worked as a medical emergency manager.
Temperatures skyrocketed that year in the Pacific Northwest. The metal joints on the roads expanded until roads broke, crops broke, and hundreds of people died. Shocked by his experience, he brought a new perspective when he returned to Albuquerque. After 10 years away, the place was not the same as when he left it.
In 2022, the Rio Grande stretch through Albuquerque became dry for the first time in his life, and wildfires were more common than before. If that wasn’t enough, the bark had invaded the tree of heat stress, he said.
Matthews-Trigg also found that cooling devices such as swamps and evaporation coolers can no longer handle rising heat, prompting residents to switch to air conditioners and heat pumps.
Nationally, almost 90% of American households acquired air conditioners in 2020, less than 80% of the beginning of the century, according to the Energy Information Bureau. USA Today previously reported that Americans are seeing higher bills in the summer as they use more air conditioners to cool down from rising temperatures.
Air conditioners use more electricity, but people don’t have another option because old cooling technology is no longer effective, said Matthews-Trigg, founding board member of Healthy Climate New Mexico.
“You get a temperature that rises to 105, but if you cool the air up to 85 degrees, it’s still too hot,” he said.
In Albuquerque, city officials recently passed a new law that requires rental properties to have cooling systems.
State officials are also proposing workplace protections where employers need to incorporate breaks and cooling areas, reports NM, a nonprofit newsroom source.
Other states like New York and Oregon are also adding guidelines to protect workers during high temperatures.
Concrete jungle requires tree canopy
City tends to be warmer than its surroundings due to what is known as the city’s heat island effect. Dense tall buildings and asphalt absorb and retain heat, but heat from vehicles and air conditioners add to it. Unlike rural areas, cities have less vegetation that provides cooling and shade. The result is a more hot environment. Researchers at the Houston Advanced Research Center have partnered with government agencies and volunteers to map temperatures in the city. In 2024, they discovered a 14-degree Fahrenheit difference between the coolest Houston neighborhood and the warmest area.
But there is one effective tool to make it a little hot: trees.
Several cities have established tree planting programs. For example, New York City has planted thousands of trees to achieve its goal of reaching a 30% tree canopy to reduce the city’s heat island effect, but Austin sees more heated days and plans to have a 50% canopy cover.
The map below shows today’s thermal index forecast. For a more detailed look at how things are changing in your area, Please see this dashboard.
Volunteers from Austin nonprofits like Treefolk and Go Austin/Vamos Austin (GAVA) provide assistance.
“The best thing to do is plant trees, plant trees, plant trees,” said volunteer Maria Morales. “As mentioned in the saying, green is life. There is no tree, so there is no oxygen, no shade, none.”
Yoaly Santana Ochoa, another Gava volunteer who worked outdoors in the landscaping, said he was worried that some of Austin’s residential developments might come at the expense of cutting down trees.
“We used to have more forests. It felt fresh in those areas,” she said of the area where she works. “A little by little, we destroyed the small nature we had left behind.”
Austin and Houston are currently experiencing more than 24 days, over 90 degrees than in 1985, but cities have an average increase of more than 10 days.
