45 degrees is at the low end of the scale for a 7mm wetsuit. We are all made different so our tolerance of cold water cannot be really set or standard from one diver to the next. You would have to consider several things from your BMI to climate conditioning. A hood will certainly help. Gloves and boots would be important. I diving skin under the wetsuit would not hurt either. Plus there are 2 types of divers, Those who pee in their wet suit and those who lie about it. This can help to warm you temporarily but also rapidly cools. Drink alot of water and be ready to get warm after getting out. Once you start your accent and hit that fist thermo you can feel the warmth. It actually stings my face a little. Also be sure to watch your air you will use more air at depth plus being cold adds to air consumption. It is reccomended to end the dive if you begin to shiver uncontrollably. This is how you will know if you are in the danger area. Shivering also further cools the body. If you begin to do this or get a bad "ice cream" headache accend slowly until it subsides.