Do the Rotating types of roof turbine vents have to be covred in the winter? Does their large open spaces between the vanes allow rain and/or snow entry?
I am not a great fan of such roof vents and find that many are rusted out and don't turn. Many of the ones that do turn tend to make a lot of noise.
The chances of water and snow entry increases when they don't turn, but that is not a common problem. Having them open in the winter is very important. That's the time when moist warm air from the inside of the house can condense on atrtic surfaces and cause fungal wood rot damage.
Please see our page on roof venting.