It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When the heat is intense, pray the prayer when it is cooler (delay it), for the intensity of the heat comes from the breath of Hell. The Fire (of Hell) complained to its Lord and said: 'O Allah, parts of me are devouring other parts.' So Allah permitted it two breaths, one breath in winter and one breath in summer, and the severe heat and cold that you feel are because of this."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2055