Abu Khaldah (may Allah have mercy on him) said: I heard Anas bin Malik (may Allah be pleased with him) say that when it was cold the Prophet (peace and blessings be upon him) would pray early, and when it was very hot he would delay the prayer until it was cooler, meaning the Friday prayer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5678