Glastonbury kicks of later as the opening acts take the stage.
Reformed boy band East 17 will play the Dance Lounge along with will old-school dance duo Altern-8.
The pair will delight those nostalgic for the 90s rave scene - although it is not known if they will be wearing their trademark chemical suits.
The folk-tinged tunes of hotly-tipped Alessi's Ark provide a calmer option while popular alternative rockers Maximo Park should ignite the crowd.
Weather forecasters have predicted a "quite reasonable" start with bright sunshine but warned of the threat of of thunderstorms as the day goes on.
Weatherman Rob Hutchinson said: "The majority of the day is looking quite reasonable with warm sunshine. The problem is later. Clouds will increase throughout the day and there is the small chance of one or two heavy showers or thunderstorms. I don't want to go overboard. There is a slim chance."
Friday and Saturday will see a greater risk of storms and downpours in between sunny spells.
Mr Hutchinson added: "There's definitely the risk of heavy downpours at some point. But the chance of Glastonbury becoming a real mud-fest is low, especially with the new drainage system."
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