6 hour lures
I heard that lure spawns are locked in once the lure is activated at a stop. So if a lure is started before this event swinubs will not spawn with those lures. This would make cd disappointing if true and people lured up stops before the event thinking they will last 6 hours and thus through the event anyway
Answers
Personal experience of game mechanichs. I live one block away from the main park in my city, full of lures all day, so this situation happened to me in previous CD. The lure is settled. Half an hour or less is not bad, you put a lure when it finish and CD mons make an appearance with the new lure. But this situation is gona be different.
Something that is much more common: nests. If you go minutes before the CD starts and the pokemon nest pop up, they won't change after the CD begins. Of course mechanichs can change, im telling you what happened until today. Hope I'm wrong pal