Again, no. As long as you can replenish water and electrolytes, you’re not going to die. It doesn’t take a few hours to kill someone by heat. If you are actually unable to regulate your body temperature, your core temperature will increase much faster than “taking a whole day”. It’s the loss of water and electrolytes that inihibits your metabolism and cooling that makes you die, not the heat taking several hours to permeate through your skin. (Human metabolism generates a lot of heat, so this idea is even more absurd if you think about it).
Read a physiology textbook, or even basic evolutionary biology if a human couldn’t survive 40C with humidity, humans would be extinct.