The Empire State Building is open until 2AM. We arrived on Sunday around 11PM. Luckily for us, the skies had finally cleared (there was zero visibility from the top earlier that day).
There was absolutely no line for tickets. We walked right in. Tickets to the 86th floor are $25, and you can pay an extra $17 to go to a higher viewing platform. We stuck with the $25 ticket. They also advertised $50 passes which let you skip the lines, but there were no lines for us to skip. We walked right through.