When the heat is intense, delay the prayer until it becomes fairly cool, for intense heat is from the boiling and breathing of Hellfire
Authentic hadithعن عبد الله بن عُمَرَ وأبي هُرَيْرَةَ وأبي ذر رضي الله عنهم عن النبي - صلى الله عليه وسلم - أنه قال: «إذا اشْتَدَّ الْحَرُّ فَأَبْرِدُوا بالصلاة. فإن شدة الْحَرِّ من فَيْحِ جَهَنَّمَ».
‘Abdullāh ibn ‘Umar, Abu Hurayrah, and Abu Dharr (may Allah be pleased with them) reported that the Prophet (may Allah's peace and blessings be upon him) said: "When the heat is intense, delay the prayer until it becomes fairly cool, for intense heat is from the boiling and breathing of Hellfire."
Explanation
The Prophet (may Allah's peace and blessings be upon him) ordered that the Zhuhr Prayer should be delayed when the heat is intense, which is from the breathing and blaze of Hellfire, to a time when it is fairly cool, so that one is not distracted by heat and grief from submissiveness in prayer.
Source · Narrated by Bukhari - Narrated by Bukhari & Muslim
From the Hadith Encyclopedia (hadeethenc.com).