It seems with so many layers of thick cover the tabernacle would be well over 120 degrees at times.
The clouds that surrounded the camp fulfilled a four-fold purpose:
- to protect the people from the searing desert sun; (Shulchan Aruch Harav, Orach Chaim, ch. 625, Isaiah 4:6. See also Psalms 105:39)
This would possibly explain why the sun wasn't heating it up, but not the heat from the fire on the altar.