Have never had any issues with kites stored in the cold.
Well, not really cold, as in Canada and Russia but around minus 20 degree celcius ( = minus 4 F ) here in the winter sometimes.
Leave all valves open (that goes for warm conditions too - NEVER store with closed valves), and no problems
I never kitesurf when it is under minus 5 degree celcius (23F) anyways....
Snowkiting when colder, yes, but in the water, nope.
The valves will be a bit tougher to close when cold, but they still work.