Why the heat and the cold get that extreme
The Fire complained about something, and was given permission.
اشْتَكَتِ النَّارُ إِلَى رَبِّهَا، فَقَالَتْ رَبِّ أَكَلَ بَعْضِي بَعْضًا، فَأَذِنَ لَهَا بِنَفَسَيْنِ نَفَسٍ فِي الشِّتَاءِ وَنَفَسٍ فِي الصَّيْفِ
Ishtakati-n-nāru ilā rabbihā, fa-qālat rabbi akala baʿḍī baʿḍā, fa-adhina lahā bi-nafasayn: nafasin fi-sh-shitāʾi wa nafasin fi-ṣ-ṣayf
The Fire complained to its Lord and said: my Lord, parts of me are consuming other parts. So He permitted it two breaths, one in winter and one in summer.
Where this comes from
The worst heat you have ever stood in and the worst cold you have ever been caught in are described here as one exhalation each. Not the thing itself. Its breath.
The full narration
Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "The (Hell) Fire complained to its Lord saying, 'O my Lord! My different parts eat up each other.' So, He allowed it to take two breaths, one in the winter and the other in summer, and this is the reason for the severe heat and the bitter cold you find (in weather)
Source
Ṣaḥīḥ al-Bukhārī · 3260
- Agreed upon as authentic (al-Bukhārī / Muslim)