911311, your seedlings saw barely below freezing temps for a few hours each night so yes they were lucky to survive. I’m guessing the pots were on the ground getting some heat from ground that has not frozen yet. Sometimes wind at night helps prevent frost from settling on plants and sometimes high freezing winds will damage citrus more than if protected from wind. If you’re potted seedlings are allowed to be outside for many hours in sub freezing temps especially if the soil and roots in pot freeze, they will die. We’ve been relatively mild winter this season so far here other than a heavy snow storm in mid December, and have not seen freezing temps here for three weeks now. However, it’s supposed to get into the low twenties mid week, so I plan on bringing my potted hardy citrus indoors. I’ve lost a lot of young “hardy” varieties to freezing temps over the years. Your seedlings will not get tall enough to bloom in 5-10 years if they keep loosing height to freeze damage every winter. Real lemons are among the least cold hardy citrus. In Atlanta it’s too cold to grow lemons outside without protection. If you want fruit off a tree growing in the ground in Atlanta, I’d suggest getting a grafted satsuma, Meyer lemon, Ichang lemon, Changsha mandarin, sour orange, grafted on flying dragon rootstock so you can keep them dwarfed enough to cover them and heat them with space heaters when temps get below freezing. Citrus fruits during late fall and winter (November/December) and north GA can freeze in those months meaning your fruit still ripening in trees will be damaged if prolonged freeze, so need to be covered anyway. Folks in south GA and the coastal southeast can get away with protection via microsprinklers or just planting a tree on south side of house, but in our more continental climate, the fruit takes longer to ripen, shorter growing season, and prolonged freezing temps sometimes below freezing for days, we must fully cover citrus to have success with fruit production. There are no commercial citrus groves in Atlanta for a reason; too cold. You might get fruit off of citrumelo or ichangensis or maybe Thomasville or other citranges in Atlanta without more than protection from northern winds, if you harvest in November.