Amazon requires its sellers to submit Prime Day / Prime Week sales couple months in advance. Usually, Lightning Deals are minimum 15% off. However, for Prime Day/Week, they raise the minimum to 20% off. Also, when you are scheduling Lightning Deals, anything near the Prime Day / Prime Week is grayed out.
Due to the rise in sellers submitting Prime Day deals, Amazon can cherry pick the ones that are most anticipated and have the best chance for Amazon to "break" their sales record for that day. Therefore, any deals that doesn't make this cut get placed a week before Prime Day/Week. So any Lightning Deal that is available right now won't be available during Prime Day (unless Amazon decides to run the same deals during that day).
R Amazon has a limited amount of deals they can offer during Prime Day and lightning deals this week were part of Prime Day submissions. If you see something for a good deal as a lightning deal right now, it be safe to purchase instead of taking your chances during Prime Day.
Source: Friend works at Amazon