I don't know what the highest temp needs to be, but it needs to be there for more than just an hour or two. If it gets really cold it can go dormant overnight. Mid 50s is not a problem. Low 30s would be more of a problem.

Are you thinking about timing your last fertilizer application?

No I was just curious.Only thing I have left to do is putting a premergent down this weekend..This hurricane irma felt like it came from the north not from the tropics ..It got cold and still is pretty cold here.With the wind and cold rain it feels morelike lows 50's outside not lows 60's .

We had the same cooling effect here in the Texas Hill Country. It got cool and very dry for maybe 10 days.

Yeah, I noticed the coolness in Texas... it even seemed to slow the grass growth a bit. I mowed on a Thursday and returned home Monday expecting to mow again... it had barely moved, even the nutsedge I've been battling wasn't poking up. As far as I know it only made it to high 50s at night...