When first starting off in my Loyale my rear brakes make an awful squeal which goes away as I drive. I've seen a discussion on this in old posts on this site, but no solution given. Anybody know the cause and solution to this?

Check to make sure the axle nut is not loose, and that the washers are installed in the correct orientation. This may be cause by loose wheel bearings, which can be caused by loose axle nuts.

Does this noise only occur when you are applying the brakes?

Also, this may seem like an odd question, but do you happen to notice it occur more when it's more humid and/or raining outside?

It's embarrassing  loud when I first use the brakes after sitting overnight but goes away after being used a few times.No noise when brakes are not being applied. I live on the coast so its always humid but it doesn't seem to matter if its raining or hot and sunny, same noise.

It is due to a combination of brake dust in the drums as well as the drum and shoes being glazed. The humidity and cold make it worse. Pull the drums and scuff the braking surface with a scotch brite pad and do the same to the face of the shoes. Hose it all down with brake clean and put it back together. good to go....

Thanks for your advice. The wheel bearing was loose on one side. Sounds better now. Took the opportunity to repack the bearings and paint the wheel wells with undercoating as some of my dearly departed subarus have started leaking there.Found some cancer while I was down there......darn  its started already