Heat and humidity exceeded physiological survivability limits during parts of the 2024 Hajj, according to new research1 that warns climate change is increasing risks for millions of pilgrims. A separate analysis2 suggests dangerous heat is also arriving earlier in the year around Makkah (Mecca), extending the period during which pilgrims may face hazardous conditions.
Research presented at the European Geosciences Union (EGU) General Assembly 2026 and a separate analysis by World Weather Attribution (WWA) both point to a future in which dangerous heat becomes a growing challenge for one of the world’s largest annual religious gatherings.
The Hajj pilgrimage, one of the five pillars of Islam, brings millions of people to Makkah each year to perform a series of rituals over five days. Pilgrims circle the Kaaba, walk between Safa and Marwa, spend time in prayer at Mount Arafat, stay in Mina and Muzdalifah, and take part in the symbolic stoning ritual known as Rami al-Jamarat. Many of these activities involve long periods outdoors and significant physical exertion.
The EGU study, led by Atta Ullah of Weather and Climate Services in Islamabad and co-authored with researchers from Climate Analytics in Berlin, analysed temperature and humidity conditions during the 2024 Hajj using sub-daily observational data and climate model projections. The findings were presented at the EGU General Assembly 2026, held in Vienna from 3–8 May.
Survivability limits exceeded during the 2024 Hajj
The researchers found that physiological survivability limits were exceeded for several hours on each day of the 2024 pilgrimage, even for healthy adults aged 18–40. On 17 June 2024, the combination of heat and humidity remained above survivability thresholds for approximately four consecutive hours.
“Our analysis shows that on June 17, 2024, the combined effect of heat and humidity breached the survivability threshold for even young, healthy adults for approximately four consecutive hours. During this period, the human body cannot maintain a safe core temperature through sweating alone, making unshaded outdoor exposure life-threatening,” said Atta Ullah.
The study comes after the 2024 Hajj, during which approximately 1,300 fatalities were reported amid extreme heat and humidity.
Among the various stages of the pilgrimage, the Day of Arafat emerged as the highest-risk period. Pilgrims spend much of the day outdoors on the open plain of Arafat, where shade is limited and heat exposure can be prolonged. Researchers warn that this ritual could become increasingly difficult to maintain in its traditional form if temperatures continue to rise.
The study notes that some adaptations are already changing the pilgrimage environment. These include the enclosed Sa’i route between Safa and Marwa and the expansion of shelters and permanent structures in locations such as Mina. The authors argue that such measures can improve safety, although adaptation alone cannot fully eliminate the risks associated with continued warming.
Previous research suggests that in a world that warms by 2 °C, the risk of heat stroke during Hajj could increase by up to ten times. Limiting warming to 1.5 °C could reduce that increase to around five times.
Because the Islamic lunar calendar shifts relative to the seasons, Hajj will occur during relatively cooler periods for the next two to three decades. However, the pilgrimage is expected to move back into the hottest months around 2050. Climate model projections indicate that survivability thresholds are likely to be exceeded more frequently and more rapidly during future summer pilgrimages.
Dangerous heat is extending beyond the summer months
A separate analysis published on 29 May by World Weather Attribution shows that the effects of warming are already extending dangerous heat into months that were historically less extreme.
Using observational datasets covering the region around Makkah, researchers found that average temperatures during May 2026 reached approximately 31.2 °C, almost identical to average summer temperatures recorded between 1970 and 1990. Temperatures above 32 °C, roughly the average summer temperature during that earlier period, are now expected to occur in most years during May.
The analysis also found that peak May temperatures are now about 2 °C hotter than they would have been without human-caused climate change, while average May temperatures are approximately 3.5 °C warmer. Temperatures exceeding 40 °C in May, once more characteristic of June, July and August, are now expected every two to three years.
According to the researchers, dangerous May heat has become substantially more likely. Average May temperatures comparable to those recorded in 2026 would have been extraordinarily unlikely in a preindustrial climate, with the researchers estimating they are now more than 10,000 times more likely. Peak May temperatures similar to those observed today are estimated to be around 13 to 25 times more likely because of climate change.
The result is a longer season of dangerous heat exposure for pilgrims. Conditions that were largely confined to midsummer several decades ago are increasingly occurring weeks earlier.
Saudi authorities have introduced heat-protection measures including shaded walkways, cooling stations, misting systems and expanded medical services. The WWA researchers note that these efforts have helped reduce heat-related illnesses, but they also point out that access to food, water, cooling infrastructure and medical support may not be equal for all pilgrims, particularly those travelling without official permits.
The future risks could be considerably greater. Citing previous research, the WWA analysis notes that if global temperatures rise by 3 °C by the end of the century, a level broadly consistent with the trajectory implied by current climate policies, around 97% of Hajj pilgrimages could occur during periods when dangerous heat levels are expected in Makkah.
Taken together, the two studies suggest that climate change is affecting not only health and safety during Hajj but also the conditions under which one of Islam’s most important religious practices is carried out. Researchers conclude that adaptation measures can reduce some risks, but limiting future warming remains essential to protect pilgrims and preserve the traditional practice of the pilgrimage.
Reference:
(1) Ullah, A., Sadad, A., Saleh Khan, M., and Saeed, F., ‘When Faith Meets Heat: Climate Change Risks During the Hajj Pilgrimage’, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21325 (2026). DOI: 10.5194/egusphere-egu26-21325
(2) Clair Barnes and Friederike Otto, ‘Climate change exposes millions of Hajj pilgrims to deadly heat for increasingly longer parts of the year’, World Weather Attribution (2026)
Article Source:
Press Release/Material by EGU General Assembly 2026 & World Weather Attribution (WWA)
Featured image credit: Haidan | Unsplash
