A statement on the festival's website and social media said: "The potential risk was too severe for Sunday to go ahead. We are very sorry for the disappointment and disruption caused to everyone who was looking forward to the final day of the festival."
"We advise people to pack their tents and belongings and leave the site calmly over the course of the day."
But festival goers have taken to social media to voice their dismay with the way organisers have handled the wet conditions, saying the festival seemed unprepared for poor weather.
"Many tents robbed, rampaging underage drinkers, so many kids on drugs, designated family areas with no one to supervise who camps in them," said one Instagram user.
"Disaster of a VIP area, no campsite security posts whatsoever, plenty of mud; the good squishy sticky deep stuff, changing all of the set times and moving acts around without sticking up a couple of signs to let anyone know. I could go on."
Another attendee posted a "bit of a rant" on Twitter, in which she criticised the festival for its poor security and changing of set times.
A bit of a rant about Ynot festival. (I feel awful for moaning so much but maybe you could learn from it in the future). @Y_Not_Festival pic.twitter.com/xNQhx3377h