Why Some Heat Waves Are Deadlier Than Others

Men drink water on Duomo Square next to Milan’s Duomo Cathedral after temperatures rise during a heat wave on July 21, 2022 in Milan, Italy. – Reuters
  • Europe’s heat wave saw almost 1,700 extra deaths recorded in England and Wales in just one week.
  • When and where a heat wave occurs makes a difference.
  • Those living in poor communities and the homeless are at greater risk.

LONDON: Europe’s record-breaking heat wave last month saw almost 1,700 extra deaths in just one week in England and Wales, with Portugal and Spain adding another 1,700, according to preliminary figures.

The figures, which are likely to change as records are updated, give the first indication of heat deaths as temperatures from London to Madrid hit around 40 degrees Celsius or more.

Figures for England and Wales released by the UK’s Office for National Statistics on Tuesday count the number of deaths registered between July 16-22 compared to those expected over the same period, based on a 5-year average of deaths. On.

The World Health Organization toll for the Iberian Peninsula is also tentative.

But July’s figures came nowhere near the 70,000 heat-related deaths during the European heatwave in 2003.

Here are some factors that make some heatwaves more deadly than others.


When and where a heat wave occurs makes a difference.

In the first two weeks of August, the 2003 heat wave shut down businesses, wiped out crops and dried up rivers.

The Paris region of France has felt the worst impact. Heat waves are more intense in cities because concrete and asphalt absorb and retain heat.

The peak coincided with the traditional holiday period, when many children were out of school and families on the day off, in some cases leaving elderly relatives behind.

Of the nearly 15,000 people who died in France, more than 11,000 were over the age of 75.

“A lot of people said goodbye to grandma sitting in her house and went on vacation,” said Matthew Huber, a global expert on heat stress at Purdue University. “Normally, there would be people checking in”.

The doctors were also on leave. “Emergency services were not as prepared, and they didn’t have people to call,” said Mathilde Pascal, a researcher at the French Public Health Agency.

France is now baking into its third heat wave of summer 2022, affecting wildlife as well as humans.


After the 2003 disaster, many European countries created heat wave action plans and began issuing early warnings. Experts say preparing for extreme heat can save lives.

“More and more people know what to do in response to a heat wave,” said Chloe Bremicombe, a heat wave researcher at the University of Reading in the UK. But some countries are better equipped than others: According to US federal statistics, about 90 percent of American homes have air conditioning, compared to only 20 percent of European homes.

But technology can’t always help. This year, Palestinians living in the crowded Gaza Strip have been enduring a sweltering summer heat wave made worse by power cuts that have left them without electricity for up to 10 hours a day.

Nearly a third of the US population was under a heat warning last month, with forecasts predicting more intense heat this month.

Those living in poor communities and the homeless are at greater risk.

Of the 339 people who died during last year’s heat wave in Phoenix, Arizona, 130 were homeless, local health officials said.

Some US cities, including Phoenix, have hired “heat officers” to help communities cope by handing out bottled water or directing people to air-conditioned cooling centers.

“The risk of heat-related death is 200 to 300 times higher among our homeless neighbors than the rest of the population,” said Phoenix Heat Officer David Hondola.

Physiological response

People who live in countries with hot climates are usually used to high temperatures. As a person is repeatedly exposed to high temperatures, they develop a lower heart rate and core body temperature over time, improving their endurance.

So the temperature at which people start dying from heat illness varies by location, as does the relative “minimum mortality temperature” (MMT) when all deaths from natural causes are at their lowest. They reach

“If you’re living in India, the MMT is much higher than if you’re in the UK,” Huber said.

Recent research also suggests that an area’s MMT may increase as it warms. For every 1°C increase in average summer temperatures in Spain between 1978 and 2017, for example, scientists found a 0.73°C increase in MMT, a study published in April in the journal Environmental Research Letters found. was

But with so much still unknown about extreme heat and human tolerance, scientists aren’t sure whether the changes they’re seeing in MMTs over time are related to people becoming more aware of the risks, or to them. It can also be better equipped to cope.

“There are many possible explanations, and we don’t yet know which is the most important cause,” Huber said.