Originally Posted by
envane
Its been a hot summer and all, but I doubt its been 90 degrees anywhere in North America at 4 AM.
Can't say for sure about 4AM, but it was definitely over 90 as late/early as 1:30 AM in the DC area several times this summer. I believe the 'lows' those days were in the mid to high 80s. Can't say for sure, but wouldn't rule out 90s overnight in more southerly but still urban climes.