shouldn't be too bad. I'm pullin the absolute extreme on temps and my flowers are doin just fine. night time temps are about 60-65 and during lights on my temp gets up to like 90-95. besides a little purple in the stems there all doin just fine. as long as the temps dont get down into the low 50's and lower I think it's fine. Its not optimal but yet again I am using miracle grow soil. I wouldn't be too worried bout it unless you notice that they slow down growth dramatically. Just keep and eye on em and if you are worried then try using a space heater on the intake side of your fan to up the night temps a bit. :thumbsup:

Just think of those occasional cold summer nights where the temp gets down to the 50's(nature). In the end its a weed and it ain't that bad.