I am not picking on anybody on here, But I get this question on other sites at least weekly, as long as you are dealing with Coturnix (Japanese) or New World Quail (Bobwhite, valley, gambel, blue scaled etc..) Then They will be absolutely fine. As long as you provide them with a roof and a wind break they can survive frigid temps, My birds did fine in -20F last winter. Just always let them have feed and water, because digestion provides warmth. Do NOT give them a heat lamp or any artificial heat unless they are in a insulated building, the reason being, you birds will be naturally hardier without it, and if you do provide it, and a circuit shorts or the power goes out when its very cold, your birds will be acclimated to the warmth they have been receiving and will likely die from the temperature shock and not being acclimated. I dont worry about my birds in the cold, never have had a problem with it. Just provide the necessities, and they will take care of themselves