Heat is a growing threat to the Hajj—even in spring

Temperatures during the pilgrimage in Saudi Arabia are rising as climate change accelerates, according to a growing body of research.

This article originally appeared on Inside Climate News, a nonprofit, non-partisan news organization that covers climate, energy and the environment. Sign up for their newsletter here.

More than 1.7 million people participated last week in the annual Islamic pilgrimage to Mecca in Saudi Arabia—consistently one of the world’s largest mass gatherings. 

Muslims are expected to perform Hajj at least once in their lives, but an increasingly perilous threat looms over the holy journey: heat. 

When the Hajj took place in mid-June during 2024, more than 1,300 people died, many succumbing to heat-related illnesses as temperatures topped 125 degrees Fahrenheit and humidity hit unusually high levels. The pilgrimage’s timing changes each year based on the Islamic lunar calendar, so this year—and the next roughly two decades—fall in cooler seasons, a slight relief for pilgrims and officials helping manage the pilgrimage. 

However, a new analysis suggests that the window for heat-safe Hajj pilgrimages is dwindling as climate change ratchets up the temperature during historically cooler months. Research shows that the region’s growing suite of heat-mitigation strategies for the pilgrimage significantly reduces health issues. But experts say worsening heat may outpace these efforts and the key to tackling this issue is addressing the source of the problem—carbon emissions.

A Sizzling Holy Journey

One of the five pillars of Islam, the Hajj is considered a mandatory religious duty for Muslims who are physically and financially able to complete it. The five- to six-day pilgrimage can cover dozens of miles through parts of the Saudi Arabian desert region, with visits to holy sites along the way. 

The majority of participants are traveling to the country from other parts of the world, and many are older than 65—factors that can make them particularly vulnerable to heat stress.

Visitors exposed to much higher temperatures than they’re used to are not adequately acclimatized. So until their bodies adjust, heat and humidity can affect them physiologically more than residents. (I previously reported on this phenomenon with tourism.) Elderly populations and people with illnesses face higher risks during the Hajj, particularly in conditions such as 2024’s sweltering journey. 

A study published last year found the upper limits of human heat tolerance were topped for a total of 43 hours over the six days of the 2024 Hajj, which would be difficult for people to handle even in peak physical condition. 

In recent years, Saudi Arabia has introduced heat-action plans with interventions such as more shade, free water and umbrellas, air-conditioned buses and misting areas. A 2024 study analyzing heat and health during the Hajj over 40 years found that heat-mitigation strategies helped significantly reduce cases of heat stress and exhaustion. 

But not everyone has access to these measures, an issue made abundantly clear in 2024, experts say. According to the Saudi government, the vast majority of pilgrims who died during that year’s Hajj were not registered for the pilgrimage. Without permits, they were not allowed to tap into certain cooling resources, The New York Times reported. It can be difficult to secure a Hajj permit due to high demand, quotas and costs. 

And even for permitted participants, heat plans may not cut it much longer. The 2024 study analyzing decades of data suggests that “the intensifying heat may be outpacing current mitigation efforts, signalling a need to recalibrate existing approaches.” 

Summer in Spring  

Though this year’s Hajj was held in spring, it was still a scorcher. Temperatures consistently passed 100 degrees.

“I can’t adapt,” Inas Gamal, a Hajj participant traveling from Egypt, told France 24. “I had planned to perform all my prayers at the Grand Mosque, but I couldn’t go down for the prayers held during the day.”

This year’s temperatures may not seem staggeringly hot compared with the peak 125-degree day during the 2024 Hajj, but it’s much hotter than it used to be this time of year, according to the new analysis by a team of scientists with World Weather Attribution. The researchers found that average daily temperatures in Mecca and the surrounding region this May were almost as high as the average summertime temperatures from 1970 to 1990. This level of heat is much more likely than it would have been in a preindustrial climate, according to the scientists. 

“Climate change has once again shown us that expectations based on a climate that no longer exists can be thrown out of the window,” analysis co-author Clair Barnes, a climate scientist at Imperial College London, said in a statement. “Our analysis shows very clearly that less of the year is now safe for the millions of Muslims who wish to undertake the Hajj.” 

The Hajj is not set to take place in the summer months again until around 2050, but that doesn’t mean participants are safe from extreme heat in the fall and even in spring before then, the new study suggests. And as the Guardian pointed out, Saudi Arabia is the world’s second- largest oil producer, supplying climate-warming fossil fuels to the rest of the world. 

“If we don’t rapidly reduce our dependence on fossil fuels — an industry at the very centre of the Saudi economy — we are resigning ourselves to the fact that millions and millions of Muslims will be forced to carry out the Hajj rituals in a climate that is simply unsuitable for it,” analysis co-author Friederike Otto of Imperial College London said in a statement.