On November 23, 1963, the day after President John F. Kennedy was assassinated, Bobby Hebb’s brother, Harold, was killed in a knife fight. Deeply overwhelmed with grief at both deaths, Bobby found solace in his songwriting. According to Wikipedia, Bobby said this about the song:
“All my intentions were just to think of happier times – basically looking for a brighter day – because times were at a low tide. After I wrote it, I thought “Sunny” just might be a different approach to what Johnny Bragg was talking about in “Just Walkin’ in the Rain“.
The song was released in 1966 and rose to #3 on the R&B chart, #2 on the Hot 100, and #12 in the UK. Bobby went on tour with The Beatles in 1966 and at the time "Sunny" was higher on the charts than any concurrent song by the Fab Four. BMI ranked it #25 on their list of "Top 100 Songs of the Century."