Lake Placid has been running nightly lows in the low 50's, and I'd expect that temps at the shelters and campsites might be 5 degrees cooler (no more; there's no camping above 3500 feet elevation at this time of year). There's always the possibility of a sudden cold snap, of course.
It's been a very wet year, and the trails have been extremely muddy. The exception is the high ridges, such as the Great Range Trail - all such ridges are bone dry and you sometimes have to lose a thousand feet of elevation to get down to where the springs and streams are. But once you're down off the ridge, the whole place is beaver swamp, and the answer to "where's the next water source?" is likely to be, "you're standing in it."
My maps have more detail about water than the old topos, NatGeo, or Google. You can see that there's water everywhere.
I'm looking forward to getting back on trail. I'm planning the short section from Wakely Dam to Long Lake on the 17th and 18th, as a shakedown to see whether my knee is up to more. It's had me out of commission for about a month. (Memo to self:
Don't fall down and sprain a knee when the nearest highway is 15 miles away!) That'll finish up the last part I missed in my unsuccessful thru-hike.