well unless your in extreem northern florida its not gonna get cold enough to really damage it.
florida is good. from the pics im guessing some strain of sativa, which has a longer flowering cycle on average.
dont really worry about a plastic bag unless you know theres a frost coming.
you dont normally get plant damage untill mid-low 30's, above that your just talking minor growth stunting.
you might try and get it more direct sunlight though.