No, it isn't, I'm afraid. We use 'unclear' to mean that something is difficult to understand, for example, 'It's unclear what you are trying to say'. For the day, you could say: Cloudy Overcast Dull

I generally don't hear anyone call it an "unclear day". I would use "cloudy day" if the sky is cloudy or "foggy day" if there is a lot of fog. Also the sentence should be written "On a cloudy day in June, I was waiting for someone" or (for more clarity) "I was waiting for someone on a cloudy day in June" Hope this helped :)

was June, I was waiting for you in obscure day. may be so ))

nope its not true. unclear is something about the situation not directly related with day.