STORY: Nearly 2 million Muslims will complete the haj pilgrimage this week, but extreme heat has been fatal for hundreds who started the journey last Friday, to the Kaaba in Mecca, Saudi Arabia.

According to reports, at least 562 people have died during the haj.

Egypt has reported 307 deaths and 118 missing, with temperatures hitting over 124 degrees Fahrenheit.

The haj's timing is based on the lunar year, moving back 10 days each year.

While the haj is now moving towards winter, it will occur in the peak of summer in Saudi Arabia by the 2040s.

Climate scientist Fahad Saeed says these deaths hint at future risks for millions of haj pilgrims.

"We need to prepare, we need to adapt, we need to introduce the adaptation option as much as we can. While realizing that it will compromise on the centuries old ritual, but still we need to save people. But at the same time, we must do climate action to stop the global warming at 1.5 degrees centigrade. At anything beyond that, we are putting those pilgrims at the risk of death."

Heat-related deaths during the haj have been recorded since the 1400s.

Pilgrims' vulnerability stems from exertion, exposure, and older age, as well as a simple lack of acclimatization to the heat.

According to Saudi officials last year, more than 2,000 people suffered from heat stress during that haj.

A 2021 study in the journal Environmental Research Letters found that if global temperatures rise by 2.7 degrees Fahrenheit above pre-industrial levels,

heat stroke risk for haj pilgrims will increase by five times.

Still, pilgrims remain determined - for some, it's a one-in-a-lifetime affair.

"Haj is the fifth pillar of Islam and it is a mandatory duty for every capable person. So you have to exert efforts and get tired. Haj is a difficult task, so you have to exert efforts and perform the rituals even in the conditions of heat and crowding. You use an umbrella, drink water and pour it onto your body to prevent dehydration. And the water sprinklers in the walkways help."

In 2016, Saudi Arabia implemented a heat strategy with shaded areas, water points at every 500 meters, and improved healthcare.

Saudi health authorities advised pilgrims to stay hydrated and avoid outdoor activities from 11 a.m. to 3 p.m. during this year's haj.