I'm guessing, are you south of the equator? If so, that means your winter is just about to begin. Also the temperatures you are describing are in celcius and not fahrenheit. If that is true your winters are about the same, temperature wise, as ours here in Tucson, Arizona, USA and some parts of northern Florida, USA. I keep my SBB (Screened Bottom Boards) open all year long and have had no problems from that.