Inclement = Bitter, Nasty

I have used the word inclement for many years, not really knowing what it meant. Is it a happy euphemism for "rainy"? I don't know. So finally I thesaurus.com-ed it and discovered that it means "Bitter and Nasty." That makes a lot of sense, but why don't we call it what it is? If my flight gets canceled, I would rather it be because of life-threatening "bitter and nasty" weather conditions, not because of something that sounds like a geriatric medical condition. Think about it...