Despite the scorching heatwave, thousands of Shia mourners participated in the Muharram procession. Muharram is the first month of the Islamic calendar and is considered one of its holiest months. Shia Muslims observe Muharram as a period of mourning in remembrance of the martyrdom of Imam Hussain, the grandson of the Prophet Muhammad (PBUH). Imam Hussain was martyred on the 10th day of Muharram, known as Ashura, during the Battle of Karbala in 680 A.D.