Breeds That Handle Heat & Cold Weather

A lot is similar to humans, accumulation has a lot to do with it.
Heat index of 104°f and wind chill of -40°f, are not that uncommon here and I have a English Mastiff, but we are out walking everyday.

Any double coated breed will do well with the cold, the try is accumulation to the heat.
Same as a single coated would do generally better with the heat and need a sweater for the cold.

If your looking at something that would take both more naturally, I would say a Boerboel, they take the heat of South Africa and do well in the Mountains of Colorado in winter.

I would not say it is a breed for very many people though do to energy, size, drool, and temper.

It depends on what you mean by "handle." Like... live outside with adequate shelter? Be willing to potty outside? Be able to walk around the block? Or have a super active lifestyle in hot and cold?
I think most healthy, moderately built dogs can handle anything, with common sense safety in mind. For example, I wouldn't say... Do a 10 mile exposed/dry hike with ANY dog in 90+ degree weather no matter how active or athletic they are. I wouldn't walk a malamute in a blizzard. And when I say "moderate" I mean not too much or too little of anything. Not too huge or too small, not too fluffy or too thin coated, not too brachy...

I have a rottie/retriever and a Dutch shepherd and they can both handle anything. Neither dog enjoys hot weather but will still play in it (my Dutchie will probably go until he dies of heat stroke if I let him). And I compensate by doing stuff earlier in the day when it's cooler, playing in water, spraying them with hoses, etc. They both adore the cold.