I set my limit at 40 degrees.
I have a pair of flip mitts. the top section of the fingers flips open. Keeps hands warm and dry but can't do anything but paddle with them on. The flipped back portion just gets in the way.
I have not really found anything I can fish with and keep my hands warm yet. chemical warmers do not do the job when out in the cold. old style hand warmer with the charcoal stick do not produce enough heat when in the cold. Scared of liquid fueled hand warmers.
As for what people wear in the cold you might want to check out the following
Cold weather kayak gear for north texas for in the kayaking forum. On this thread also be sure to look down a few posts for post from Todd on 10/8/18 with the video for :Exploding the Waders Of Death Myth"
Cold Weather Gear in the bass fishing forum.
You need to be concerned about not just staying warm, but also what will help keep you alive if you do take a spill in cold water and/or cold temps. Taking a spill with wrong clothing will kill you quickly. Temps changing suddenly can often be accompanied by high winds which again increases chances of getting wet or capsizing. If winds increase beyond point where you can get back you could be out there for a while. Also sudden temp change can bring rain.
During winter, once the sun sets it cools off pretty quickly also. Been out feeling very comfy then not long after sunset feeling pretty cold and really glad to be in heated vehicle after getting back to ramp and loading up my stuff.