I have a stock reply which goes, "I'm fine thanks but isn't it hot/cold/windy/rainy/ etc." Whatever the weather is just substitute the appropriate prevailing conditions. That deflects the conversation away from the personal and onto the far more acceptable, but irrelevant, social niceties.
I accept this may be an issue if you live in a place where the weather is quite constant, but then I would simply say, "I'm fine thanks, but isn't it hot, what are the chances of a blizzard!?!" Now in Arizona or such like that is unlikely
, but you pass it off as a joke and it gives them a chance to say, "Well if you recall a few years ago, now that was a hot one!" etc.
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Moomintroll sighed. He felt sad even though he had no real reason to feel that way.