The Stanford Encyclopedia of Philosophy has an article on vagueness that struck me as odd because it seems to assume that vagueness is a property of only certain kinds of propositions or predicates, while to me it is fairly clear that practically all empirical properties have vague boundaries. The article gives examples of non-vagueness like checkers or mathematics, but those are formalisms where they push the vagueness out of the formalism and into the application. What I mean is that, sure, the rules of checkers have no vagueness, but whether a checker is in a particular square or not is vague. What if it's overlapping the edge? What if it's half in one square and half in the other? The rules of checkers avoid vagueness by simply disallowing such cases.
What kind of physical property does not have boundary conditions where it is not clear how to judge the property? Measurements, no matter how precise, still have imprecision. Even physical classifications like "this is water" are vague. What if it is 3.5% dissolved salts? Is it still water or does it become sea water? If you still call it water, what about 20% salts? Is it still water or is it now a saline solution? At some concentration of salt, it is no longer water, but what concentration that is is vague.
You might argue that although it is vague whether the contents of a vial are water or not, the actual H2O in the vial is precisely (non-vaguely) water. But once again, that's a theoretical thing, not an empirical thing. That is, you can't observe that the H2O in the vial is water; you define that the H2O in the vial is water. As soon as you move to actual empirical judgments vague boundary cases start to rear their heads.
I can't come up with any empirical judgements that aren't subject, at least in principle, to vague boundary conditions. Are there any?
ADDENDUM: One of the answers made me realize that I was not clear enough about my question. I'm not saying that there are no empirically verifiable propositions that are clearly and precisely true or false. The examples given in the answer include "The population of Birkenhead is less than that of New York" and "Elephants can't fly".
I agree that in these cases, there is no vagueness, but there is potential vagueness in the judgments as can be seen by changing the terms to other terms that are chosen to highlight the vagueness. For example: "The population of New York is less today than it was yesterday". Now the truth of the statement depends on whether a tourist is considered part of the population. What about someone who came to New York to a hospice expected to die in a few days. He moved to New York permanently, but will be there less time than the tourist. What about someone who lives half time in New York and half time in New Jersey?
For another example, "A flying squirrel can't fly". This requires deciding whether gliding is flying. If you don't think that's a borderline case, what about an animal that can mostly just glide but can flap to gain altitude but only a half inch and only once a minute or so?