nobody writes:

You *can* die from heat. You WILL die from cold.

You can and will die from extremes in either direction.

In heat, you can survive without air conditioning.

No, you cannot, beyond a certain point. You must have a way of
removing body heat, and that requires active cooling. The body's own
evaporative cooling is only reliable up to a certain (modest)
threshold of heat; thereafter, external cooling is mandatory, or
hyperthermia and death will ensue.

Drink lots, have a fan, dress properly. No problem.

See above. In high temperature and humidity, a fan and drinks will
not suffice, as they will not be able to remove body heat quickly
enough through perspiration to prevent hyperthermia.

Using a fan also raises temperature and humidity.

If you turn off your air conditioning and follow the above,
you will have gotten used to it within days.

Modern cities in hot climates cannot function without air
conditioning.

The human body is built to have its own cooling (it is
called sweat).

The human body survives by sweating only within narrow limits.

And you can survive even when outside temperature exceeds
body temperature.

Only within narrow limits and under certain conditions.

In cold, if you do not have proper clothing, you will
die and/or lose limbs to frostbite.

Yes. However, with the right clothing, you can tolerate any cold air
temperature that you are ever likely to encounter on the Earth's
surface.

And you still need to drink and eat properly. And
remember that at night, you need extra warm sleeping bag because your
metabolism slows down and you generate less heat.

You just need warm clothing, be it a sleeping bag or something else.

It is easier to learn to survive in heat than in cold.

No, it's just the opposite. You can survive cold with protective
clothing alone. In heat, you must have active cooling.

At 40°C, you are only 20 degrees from optimal temperature. But at -20°,
you are 40 degrees from optimal comfort temperature.

But at 40° C, heat must be actively removed from your body, whereas at
-20° C, you need do nothing more than conserve a portion of the heat
your body produces.

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