Global heating has "fundamentally altered" the climate of Mecca and is exposing millions of hajj pilgrims to extreme and dangerous heat even in months outside summer, new analysis has found.
The annual Islamic pilgrimage to Mecca now faces scorching temperatures of 40°C (104°F) regularly in May, a month that was historically cooler. In past decades, such peaks would only have occurred in summer. Researchers warn that without a rapid transition away from fossil fuels, hajj will take place amid dangerous heat almost all year round by the end of the century.
Climate Crisis and the Hajj
More than 1,300 pilgrims died due to extreme heat and humidity in 2024, when hajj was in June. The analysis by World Weather Attribution scientists found that 40°C is now expected in May once every two to three years as a result of the climate crisis. The average temperature for May is now 3.5°C hotter than before human-caused global heating.
"May is now as dangerous as the height of summer used to be," said Dr. Clair Barnes at Imperial College London. Saudi Arabia, the world's second biggest oil producer, has introduced heat action plans including shaded walkways, cooling stations, misting systems, and expanded medical services to reduce heat-related illnesses.
Need for Rapid Transition
Prof. Friederike Otto at Imperial College London said: "This requires more than just reactive mitigation. 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 of Muslims will be forced to carry out the hajj rituals in a climate that is simply unsuitable for it."
The hajj follows the Islamic lunar calendar, which is 10–11 days shorter than the solar Gregorian calendar, causing the dates to shift earlier each year. Over a cycle of about 33 years, hajj moves through every season. A 2022 study found that if global temperatures rise by 3°C by the end of the century, about 97% of all hajj pilgrimages would endure dangerous levels of heat in Mecca.
Dr. Emmanuel Raju at the Copenhagen Centre for Disaster Research said: "Extreme heat during the hajj presents a unique humanitarian challenge because it involves millions of people moving through an outdoor environment for days on end. Measures like misting fans and water stations are vital, but we must face the reality that if temperatures continue to climb at this pace, the health and lives of millions during their pilgrimage is at risk."
The Ministry of Hajj and Umrah in Saudi Arabia was contacted for comment.
