The song says the "sun shines bright on my old Kentucky home." But, the long range forecast from the National Weather Service is calling for showers in Louisville, Ky., on Kentucky Derby Day.The May 5 forecast is for rain and a high of 75 degrees. The previous day, when the Kentucky Oaks is run at Churchill Downs, the weather service is predicting heavy clouds and a high of 76 degrees.The 10-day forecast does not call for any rain in Louisville between today and Derby Day.Last year, when Fusaichi Pegasus became the first favorite to win the Derby since Spectacular Bid in 1979, it was 82 degrees at post time (5:29 p.m.). This year, the post time has been moved to 6:04 p.m.The last Derby run on an off track was in 1994, when it was 57 degrees and over four-tenths of an inch of rain fell in Louisville. The winner was Go for Gin.