The freezing point depression of a 12% Sodium Hypochlorite solution (which also has 9.4% salt due to the manufacturing process of chlorine) is 15.3C or 27F so the freezing point is -15.3C or 5F. So unless you are expecting sustained temperatures well below freezing (i.e. closer to 5 degrees Fahrenheit or below), then it should be safe.
The full calculation was determined from the following. 12% solution is (approximately; ignoring Trade % vs. weight % distinctions) 12 grams of sodium hypochlorite in 100 grams total. There is also 12*58.443/74.4422 = 9.42 grams of salt (from the way chlorine is produced) so that's 100-12-9.42 = 78.58 grams water. There is 12/74.4422 = 0.1612 moles times 4 for dissociation and salt (there is sodium, hypochlorite, sodium, chloride) so 0.6448 moles solute in 78.58 grams water so in 1000 grams (1 kilogram) that is 8.2 so that times 1.86 is 15.3C = 27F.