New Study: Parts of Africa, Mexico, and Southern Europe Now Endure Up to Two More Months of Dangerous Heat Than in the 1970s

What the Study Actually Measured

Most climate research tracks air temperature. This one went further.

Researchers published findings Monday in the peer-reviewed journal Nature Climate Change using something called the Universal Thermal Climate Index, which factors in temperature, humidity, wind speed, and the human body's physiological response to its environment. The goal was to quantify heat stress on actual people, not just weather stations.

Humidity is the key variable most temperature-only analyses miss. When the air is humid, sweat evaporates more slowly, which degrades the body's primary cooling mechanism. A humid heat wave can be deadlier than a dry one at the same thermometer reading.

The Numbers, by Region

Researchers defined three thresholds of heat stress:

• Strong: feels-like temperature at or above 89.6°F (32°C)
• Very strong: at or above 100.4°F (38°C)
• Extreme: at or above 114.8°F (46°C)

According to reporting by the Associated Press, parts of Southern Africa — specifically Namibia and Angola — along with East African countries including Tanzania, Kenya, and Uganda, plus portions of Mexico and Central America, are now seeing roughly 50 more days per year of at least strong heat stress compared to the 1970s.

Southern Europe is also getting hammered. In southern Spain, Italy, Greece, and Turkey, some areas are recording up to 40 additional strong heat stress days per year. Much of the broader Southern European region is logging close to a full extra month compared to a few decades ago, according to The Columbian's coverage of the same AP-sourced study.

In the United States, most of the country now experiences at least 15 more days annually of strong heat stress. Texas and Florida are approaching 25 or more additional days of very strong heat stress per year, per The Columbian.

Context from Prior Research

A separate study cited in the AP's coverage found that people globally endured an average of 41 extra days of dangerous heat in 2024 alone. Other research projects that the world could add nearly two months of extreme heat days per year by the end of the century if current warming trajectories hold.

The Nature Climate Change study's contribution is the six-decade span and the human-body focus. It catalogs what has already happened since the 1970s rather than modeling future projections.

The Skeptic's Genuine Concern

The strongest pushback on studies like this one comes from researchers and analysts who question whether modeling the human body's response to climate adds precision or just layers of assumptions on top of assumptions. The Universal Thermal Climate Index involves variables — wind speed, radiation, metabolic rate — that are harder to measure consistently across decades and geographies than a thermometer reading. Critics argue that the further a study moves from direct observation toward modeled indices, the greater the margin for compounding error.

That concern is legitimate and worth tracking. The study's authors chose a peer-reviewed methodology, and Nature Climate Change has a rigorous editorial process. Peer review doesn't make a model infallible, however. Independent replication across different data sets would strengthen the findings.

What This Means for People Who Actually Live There

Heat stress has direct consequences for outdoor workers, elderly populations, and anyone without reliable air conditioning. In sub-Saharan Africa and Central America — where the additional heat burden is largest under this study — that describes a significant share of the population. Fifty extra days of dangerous heat per year in those regions is not an abstraction.

For Southern Europe, which relies heavily on summer tourism, the economic pressure of nearly a full additional month of strong heat stress has real implications for labor, agriculture, and public health infrastructure.

The study was authored with a tag referencing researcher Rebecca Emerton, per the local10 report.

The Open Question

What remains genuinely unresolved is whether adaptation strategies (improved early-warning systems, urban cooling infrastructure, changes in agricultural timing) can keep pace with the documented trend, or whether the pace of change has already outrun the institutional capacity of the most-affected regions to respond. The data alone cannot answer that question.