I have a problem that reminds me of what you guys are talking about but it is not weather related. If I turn my tractor off and lower the front end loader to the ground. (so I am not keeping pressure on the seals.) When I first start the tractor and try to use the loader it wont work for a few minutes. After I have put the loader control in the up position for a few minutes it will work slowly and then work normal. I am sure the not working problem is air in the lines. I believe that it gets it when I allow the bucket to coast down to the ground with the tractor turned off and I think it is ingesting air at the point. If I remember to put the bucket on the ground with some down pressure and turn the tractor off then go to float mode and take the pressure off of the bucket then I dont have the problem when I go to run the tractor the next time.
Is any of the problems you are having similar to that ?