Free-fall meatbomb sites may be considered active up to FL150 when the viz is > 5 km by day or night. But that is within the demarcated area, of course. Drop outside the area, e.g. upwind on a strong wind day from altitude and, if you're outside the promulgated area, then you are far more likely to have a close encounter with a spamcanner quietly minding his own business.
A certain (not the same) local site operator announced that GA pilots should 'expect' to know that his gravity-tempters would be falling out of their aeroplane well outside the notified area on such windy days. Bolleaux, in a word. If you can't stay in the demarcated area, stay on the ground!
The antics of some Eastern European pilots - who appear barely able to understand a word of English - carrying out aerial work in this country in such circumstances I also find somewhat surprising.