Yes, the cold weather can have an effect on suspension.
That's why engine oil is multi-viscosity. That 'W' in 10W40 stands for Winter.
However, suspension oil is not multi-viscosity, so if the temperature is low enough, it can possibly affect suspension action.
And since the only heat that forks and shock generate is due to fluid and mechanical friction, traveling down the road can chill the oil even more that in the garage (esp. the forks).
So if one plans on riding during the winter, you could drain the current suspension oil and replace with lighter viscosity oil, and the reverse when it warmed up again in Spring.
And also the opposite can occur if the temperature is very high as well.
Your suspension may not work as expected if touring through Death Valley in the Summer for instance.
Last edited by SubSailor; 12-16-2013 at 05:53 PM.