Abu Hurayrah (رضي الله عنه) narrates that Rasulullah (ﷺ) is reported to have said, “When it is an extremely hot day, Allah Ta’ala turns His attention to the people of the skies and the earth. The moment a person recites the following Dua, Allah Ta'ala says to Jahannam, ‘Indeed, a servant of mine has sought refuge in me from you, now you bear testimony that I have granted him salvation from you." [Bayhaqi]

 لَا إِلهَ إِلَّا الله مَا أَشَدَّ حَرَّ هَذَا الْيَوْمِ، اللَّهم أَجِرْنِي مِنْ حَرِّ جَهَنَّم

There Is No Deity Except Allah. How Hot Is This Day! O Allah, Protect Me From The Heat Of Jahnnam.