Rear brakes locking up when rainy or cold outside?

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this is a common problem on most cars and trucks with drum brakes....in rainy and cold weather the inside of the drum gets a light amount of surface rust on the surface of the drum.... the combo of that and moisture on the shoes and drum causes them to grab and lock up..... this is also why a rig that sits for a few years with the parking brake on has locked up brakes.... I was an auto repair tech for 12 years and did lots of brake and suspension work