While today we know June as the start of the summer, going back centuries the beginning of the season has traditionally been celebrated on May 1.
The Gaelic festival of Beltane dates back to the Iron Age, and was at one time celebrated widely across Scotland, Ireland, and the Isle of Man. It is one of four Gaelic festivals marking the start of each new season—the others being Samhuinn on November 1, Imbolc on February 1, and Lughnasadh on August 1.
Known as Latha Bealltainn in Scots Gaelic, Beltane is believed to translate to 'bright fire'. The festival traditionally ushered in the start of the pastoral summer season, during which time livestock was moved to summer pastures.