More than a million Muslim pilgrims have converged on Mecca for the start of this year’s Hajj, Islam’s most important religious rite, with Saudi authorities ramping up safety measures to prevent a repeat of last year’s deadly heatwave.

As temperatures are expected to soar above 40 degrees Celsius (104 degrees Fahrenheit), worshippers, clad in white robes, were seen slowly circling the Kaaba — the sacred black cube at the heart of the Grand Mosque and the holiest site in Islam.

According to Saudi state media, large numbers of pilgrims have also begun arriving in Mina, a sprawling tent city on the outskirts of Mecca, where they will spend the night before proceeding to Mount Arafat on Thursday.

The gathering at Arafat marks the pinnacle of the Hajj, commemorating the Prophet Mohammed’s final sermon.

In response to last year’s tragedy — where over 1,300 pilgrims died as temperatures reached a searing 51.8 degrees Celsius (125.2 Fahrenheit) — Saudi authorities have introduced a series of preventive measures.

These include thousands of additional medical personnel on standby, enhanced shaded areas, and the deployment of 400 cooling units across key sites.