Thanks T&B.
I may have missled you in the way I framed the question. I am after any Hydralic System temperature limitation on the Twotter.
Some aircraft will have for example a -40C limiation on the hyraulic system for operating the flaps or a rear cargo door. This is not a limitation on the ambient temperature or a limitation on the oil but a limitation on the hydraulic system itself and I would think it relates to the internal pressure of the system due to the viscosity of the oil at low temperatures and the chance of say blowing O-rings or seals.