Precipitancy (as in, great hurry or hasty action) and precipitation (the kind that falls from the sky in the form of water) are close in spelling, but not meaning.
Although changes in the weather may come on with precipitancy (abruptness), Mom Nature probably doesn't plan it that way. Human beings, however, sometimes act impulsively, rushing headlong into a situation before thinking it through. That precipitancy can spell trouble!
Precipitancy comes into play in William Makepeace Thackeray's Vanity Fair:
"I hope there will be no women besides our own party," Lady Bareacres said, after reflecting upon the invitation which had been made, and accepted with too much precipitancy.