AWS codes usually require a preheat of the steel to around 65 or 70 degrees if the base metal is 32 or below. if you follow that, i am not sure if there are other limits for welding in cold weather. it will definitely affect the cooling rate of the weld and could definitely be a factor.
Not a problem. We do it every day. If it is structural work there some cases where pre-heating may be required.
As already stated, pre-heat is a good idea, as well as maybe wrapping the finished weld with welding blankets after if it's a critical weld.
Use a tiger torch for pre heat and sweat it out. You can purchase temp sticks if you need to be specific temp range but generally all that is needed is to sweat out. Hope this helps.
i do pipeline work and you have to preheat to 350 even in 70 degree weather nothin to do with your car though
Few yrs ago we welded a rail to the clubhouse porch with stick. It was -28 in celsius,that'll be -18 in fahrenheits. Yes,i know here are warmer days than that one was,but we just had to do it.
sure, like they said, preheat the weld area first and wrap with a welding blanket so it wont cool off to fast