 There's an old adage that says thunderstorms can cause milk to go sour. Implausible folklore? We've heard enough accounts from dairy farmers to believe something is going on. But the connection has never been scientifically proven. Experiments that have run electricity through milk have found no effect. Some theories say it's merely the warm, humid conditions which spawn thunderstorms that hasten spoilage, while others believe it's caused by ozone or bacteria carried by rainfall.