That one’s a harrowstorm bug as old as the Greymoor chapter itself. Sometimes you’ll see the scary weather visuals, even when the storm isn’t really there.
I haven’t been affected in quite a while, but I suspect the visual bug occurs client-side. I play sitting right next to my partner, and sometimes while visiting the same spot in the same zone instance, one of us would get the visual bug and the other would have normal weather.
At least until the Witches Festival the vampire lord boss could still glitch and remain unkillable despite having 0 HP until it flew high, when it'd at last die. Really old bug, almost eligible to be considered a classic.
Imperial DK and Necro tank. PC/NA
"Nothing is so bad that it can't get any worse." (Brazilian saying)