Forty Days and Forty Nights is a blues song recorded by Muddy Waters in 1956 for Chess Records. Written by Bernard Roth and produced by Leonard and Phil Chess, it was released as a single with All Aboard as the B-side and runs 2:51. The midtempo track was cut in Chicago in January 1956 during Pat Hare's first session with Waters, with Little Walter on harmonica, Willie Dixon on bass, and a lineup that likely included Fred Below or Francis Clay on drums and Jimmy Rogers or Hubert Sumlin on second guitar. The lyrics describe a lover who has left town, with the refrain Forty Days and Forty Nights and a line about sun shining while rain keeps falling. It spent six weeks on the Billboard R&B chart, peaking at number seven, and has been covered by many artists. The song later appeared on Waters' The Real Folk Blues compilation (1965) and was rerecorded for the 1969 Fathers and Sons album, with further releases including the 2009 Authorized Bootleg: Live at the Fillmore Auditorium November 4–6, 1966.
