Michael Ash writes:

This is completely ridiculous. I assume you just took 20C as an average,
then added and subtracted. You can't do that!

Sure I can. Twenty degrees Celsius is not only close to the average
temperature of the planet, it is also roughly the ideal temperature for human
habitation, according to studies I've read. Minus twenty is forty degrees
below that; therefore the hot-weather equivalent would be forty degrees above
that.

60C is higher than the
hottest recorded temperature on the planet. -20C is routine and common in
a great many inhabited locations. They're absolutely not equivalent.

Their incidence is unrelated to their survivability.

The reason that there is more cold weather than hot among human beings is that
it's far easier to survive in cold weather. A species with an ideal
temperature of 0° C would not be able to survive in an environment with a
maximum of 50+ degrees. Because all living species must shed heat, their
ideal "operating temperatures" are skewed towards the high end of planetary
temperatures by evolution. This in itself shows that heat is more dangerous
than cold.

Of course you can. You can wear light clothes, carry shade, and drink lots
of water.

That will not help in extreme heat. The laws of thermodynamics prevent it.
You can survive in extreme cold with insulation alone, by conserving the heat
that your body continuously produces. But you cannot survive in extreme heat
without actively shedding body heat, and beyond a certain temperature, that
cannot be done quickly enough to maintain core temperature, and you die.