If you can't fly by visual reference, you're on an instrument flight. Doesn't matter what the official viz, ceiling, or day of the week-if you haven't got adequate reference to control the aircraft, you're IMC. If you're not instrument proficient and adequately equipped, you stand a good chance of not completing the flight, darkness or daylight.
If you are able to control the aircraft adequately with visual reference only, then you're vfr, irregardless the official wx status. Hovering from 1 pad to the next in 100 foot vis would be a vmc flight, if you could make me do it.
Rules that allow us to something shouldn't mean we do it routinely.