As for the worst in the country, New Yorkers can at least take cold comfort in the fact that it's physically located in New Jersey, even if it does serve the whole tristate area. Congratulations to Newark Liberty Airport, a contemptible circle of hell that somehow manages 66.5% on-time arrivals -- barely enough for D-minus.
As far as this list goes, the best airports in the country are located in Hawaii. Maui's Kahului Airport topped the list at 88%, with Honolulu Airport following with 86.5%. Sunny Hawaii is about as far from NYC as you can get, so it makes sense.
To arrive at these numbers, MileCards.com looked at Department of Transportation data between 2007 and 2016. They crunched the numbers for the 50 busiest airports in the country across 10 summers, finding that 40% of those airports have more flight delays in the summer than the winter. (This makes sense given how seemingly minor shifts in temperature can affect planes.) They also found that June is the most-delayed month of the year, by a long shot: 76% of those airports have more delays in June than July or August.