Temperatures were forecast to exceed 40 degrees Celsius this week as one of the world's largest annual religious gatherings officially commences on Wednesday. 

The haj, one of the five pillars of Islam, must be performed at least once by all Muslims with the means.

As of Friday, more than 1.3 million pilgrims had arrived in Saudi Arabia for the multi-day pilgrimage, according to officials. 

This year, authorities have mobilized more than 40 government agencies and 250,000 officials, doubling their efforts to mitigate heat-related risks following a lethal heatwave in 2024 that left hundreds dead.

Shaded areas have been expanded by 50,000 square meters, thousands more medics will be on standby, and more than 400 cooling units will be deployed for the duration of the haj, Saudi Arabia's hajj minister Tawfiq al-Rabiah told AFP last week. 

The latest artificial intelligence software will also help monitor the flood of information and footage, including video from a new fleet of drones, from across Mecca to better manage the mammoth crowds.

Despite the punishing heat, pilgrims were overjoyed as they arrived in Mecca. 

"This is really a blessing from Allah," Abdul Majid Ati, a Filipino lawyer and Sharia counsellor, told AFP near the Grand Mosque.

"We feel so peaceful and safe in this place."

Abdulhamid from Nigeria, said he was "very happy" to be performing his second pilgrimage in a row at just 27 years old.

But the young man said he never walks out without his sunglasses, describing the temperatures in Mecca as "very, very, very hot".

The rites in the holy city and its surroundings fall again this year during the hot month of June.

Last year, 1,301 pilgrims, most of them unregistered and lacking access to air-conditioned tents and buses, died as temperatures soared to 51.8 degrees Celsius.

"They were caught by surprise because the intensity of the heat was so high that their adaptation measures failed," said Fahad Saeed of Climate Analytics, a think tank based in Germany.

In the run-up to this year's haj, Saudi authorities launched a widespread crackdown on unregistered worshippers -- relying on frequent raids, drone surveillance and a barrage of text alerts focused on rooting out unauthorized visitors hoping to sneak into Mecca.

Haj permits are allocated to countries on a quota system and distributed to individuals by lottery.

But even for those who can obtain them, the steep costs prompt many to attempt the hajj without a permit -- though they risk arrest and deportation if caught.

Along with hefty fines, those found illegally entering Mecca during the hajj face a potential 10-year ban from the kingdom. 

Large crowds at the hajj have proved hazardous in the past, most recently in 2015 when a stampede during the "stoning the devil" ritual in Mina, near Mecca, killed up to 2,300 people in the deadliest hajj disaster.

Saudi Arabia, which is home to Islam's holiest sanctuaries in Mecca and Medina, earns billions of dollars each year from the hajj and from pilgrimages known as Umrah, undertaken at other times of the year.

They also enhance the prestige of the Saudi monarch, who is known as the Custodian of the Two Holy Mosques of Mecca and Medina.

For Mariama, a 52-year-old pilgrim from Senegal, the journey to Mecca for the haj has fulfilled a life-long dream.

"I was dreaming about it, thinking about it every time to come here to do the haj," she said.