A buddy and I dove Canyon Lake, Texas this past December. The temp was 50 at the surface and 48 at our deepest depth (46’) of the dive. The visibility was only about 1-2’ so we did a 30 minute tour of the cars/boats and got out. The dive was fine, it was the 46 degree air temp that was a btch.
We dove 7/5mm Henderson jumpsuits, 6.5mm hoods, 5mm gloves, and 5mm boots. (Bought at LeisurePro, by the way. Nice package deal for $150)
Either way, the dive was great and the exposure protection worked well once you got past the initial shock. I would definately suggest diving with a person experienced in diving those conditions, plan your dive conservatively (and dive your plan), and go to a familiar area. Cold water can be an added stressor, so limit the "new" things you are throwing into the equation.
Most of all...Enjoy!