I guess I'm throwed off by the Celsius shit. All I'm saying is that my plants stay at 75 with the lights on and it might drop to 62 at night. This has not had an effect on my grows. Only time I had problems was when my fan broke and the temps got too high. I tried to finish the grow without another one and suffered. Once I got a new one everything has been fine since. So I guess we can agree to disagree. Although 17 degrees Celsius is probably a lot. I read fast and I was thinking F.