What areas of the world have optimum climate for humans, e.g. no extreme temperatures, no hurricanes/tornadoes/monsoons, etc., no earthquakes, no floods or tsunamis, no droughts?
My home country, Uruguay, is pretty mild.
In summer the temperature usually doesn´t go over 30/32Cº, and in winter no lower than about 0/5 at night but around 10/12 during a cold day. While there are a few instances of large flooding in some areas, most don´t know what´s that, neither hurricanes, monsoons or all the other weather extremes.
It´s geologically dead, so no earthquakes at all.
Every now and then some drough spells; but nothing oo serious neither.
No wars, riots or tin pot generalissimos (lately at least!) and relatively low crime.
It´s a rather boring place, really. 
Cape Town!
Could I propose a similar question? Where is it feasible for humans to survive without clothing or shelter? I would imagine this is the way we evolved back in the day. I suppose this would mean we’d be naked, and that it wouldn’t matter as long as it didn’t get unsurvivably hot. I would imagine this could get really high. On the other hand, I would think that it couldn’t get very low at all for too long. This is pre-fire, I mean. How cold could we take it if there were nothing to help us? With the heat, it sucks, but if we were naked it’d be survivable somehow, right? But if it were cold? I’d say not long.
I spent about 18 months on the Midway Islands in the 60’s and it has a very mild climate. Here’s a comment from one Midway web site:
Leon, Guanajuato, Mexico. No natural disasters, and even middle class and above houses don’t even bother with air conditioning for the most part.
What do you mean by “we”, Kimo Sabe? 
White folks might not be able to do so well, naked, in some geographies that darker skinned people could handle just fine.
Humans have happily survived naked for millenia on the Equator, so high temperatures simply are not an issue. Provided they have enough water a human can survive pretty much any natural temperature conceievable while humidity rmeioans below about 85%. SInce in the tropics it invariably rains and reduces the temperature well below 85% humidity we can safely say that humans can survive any natural tmeperature without clothing.
As a far as low temperatures, people in Tasmanai survived for millenia with no clothing of any sort at about the same latitude as New York City. Tasmanians also had no ability to make fire, They used fire, but coudln’t make it. Records indicate that fires went out frequently and the people stil managed to survive winetrs. So people can certainly survive without clothing or fire in regions where there is snow on the gound for weeks at a time.
Humans are pretty damn tough critters. Naked we have the broadest functional temperature range of any animals aside from some of the desert foxes. With addition of basic clothing we have the broadest temperature range of any animal.
Surely they had furs! I can’t believe anyone being able to survive snow completely naked. Maybe you can run around for an afternoon and not die of hypothermia, but you won’t survive ever going to sleep.
They had furs for use as blankets, and presumably they could wrap them around themsleves and hold them in place with their hands, but that is not clothing.
BTW, remember that the largest animal in Tasmania by this stage was kangaroo that was ~5 1/2 feet from toes to ears. The useable pelt was maybe 4’ x 3’ for an exceptional speciimen, or about enough to cover ane adult from neck to neck to waist on one side of their body. While one could have provided some protection to a walking person they would at best prostpone hypothemria for a few hours, not prevent it, and then only at the expense of being unable to collect food because you hands were occupied holding the cloak on.
Well… then they had intestines and needles to sew the pelts together to make ponchos or something. Didn’t you ever make a diorama about how clever the native americans were? Or how cavemen had coats (and feet-powered cars)?
Considering the height of a hunter-gatherer human, that sounds perfect! You just skin a kangaroo and climb on in. Pouch doubles as a hand warmer. Man, i’d even keep the ears on for camouflage.