If it is anything other than a very expensive 'sealed' then you have some water in, and it has caused a little rust. Take the wheel out hold it parallel to the ground and put a few drops of oil where the 'seal' is, spin and the oil will enter the bearings. Do this both sides.
A very likely solution...
If it is anything other than a very expensive 'sealed' then you have some water in, and it has caused a little rust. Take the wheel out hold it parallel to the ground and put a few drops of oil where the 'seal' is, spin and the oil will enter the bearings. Do this both sides.