"You can't go out like that – you'll catch a cold!"
It doesn't matter if you're wearing the attire of an Inuit, or if it's hotter than the surface of the Jupiter outside, it's highly likely that you are not wearing enough. And for god's sake don't even contemplate leaving the house with wet hair, you might as well be asking for pneumonia. And don't run or you might start sweating. Oh and have you eaten?