Yep, excess moisture trapped within the floret that doesn't get out within a couple hours will do it, especially when it's damp, cool and with little or no air circulation. It happens most when temperatures are between 32-38'F. What I don't know is exactly how biologically, what functions are prevented by these circumstances (smothering?) so as to cause such severe tissue distruction and mushiness. I think maybe you might know better than anyone, Rick. Keep in mind we're not talking about a frost or freeze circumstance/damage here.
Moby--I'll bet there weren't any mushy florets in Lincoln today at 99'F with a little wind. Maybe we'll see more of that purple leaf condition this year?
