This is the time of year everything usually changes in a period of 2 to 3 weeks. Water temps could easily drop down to around 62 or even less, depending on how cold and strong the winds are with the next couple of fronts.
If you are riding on a day that the front passes through, it could start off that day at 65 degrees and end up 50 degrees by sunset.
If you are use to that, no biggie. Most people need a pretty reasonable full wetsuit, starting real soon. I don't think a 2mm shortie is going to work, even for a Northener .
Then again, maybe you are laughing at my idea of cold (?).