Organisers hope to raise £5,000 and want people to join in the fun at The Meadows in Stamford, whatever the weather.
The festival has struggled to cover its £60,000 costs this year after losing a major sponsor and faces a £10,000 deficit.
But with 34 bands on the line-up across three stages, a massive beer festival, funfair and fireworks display, it is poised to be the best yet.
Martin Smith is chairman of the Riverside Association of Music and Arts which organises the not-for-profit event.
He said: "It is undoubtedly the best value day out for all the family and it is right on your doorstep.
"There's nothing really quite like it."
Last year's festival attracted more than 8,000 people and the organisers hope even more will attend this time.
Adults will be asked for a £2 minimum donation and youngsters aged 10 to 17 will be asked to pay £1 to help reach the target.
Martin said: "It is very tight for us. Even if we reach our target of £5,000 we will be £5,000 in debt.
"We have never been in a situation like this."
Martin thanked the volunteers who make the event possible and major sponsors Crestwood, Ideal Shopfitters and Taylors Amusements.
Secretary Jenny Collins said the outcome of this year's Riverside would determine its future.
She said: "Come rain or shine we are determined to hold the best festival the town has
ever seen. If 50 per cent of the 8,000 people made a voluntary donation of just a couple of pounds, that would make a lot of money for us."
Gabbidon, a 10-piece-band, is headlining the Riverside stage, with party punks International Trust performing on the Marquee stage and Peterborough's acoustic alternative rock band Opaque appearing on the Acoustic stage. The Prophecy True, who won the Mercury's Road to Riverside competition, will also perform.
The Acoustic and Marquee stages will both be under cover and the beer festival will be inside a 200sq ft marquee.
Festival-goers will be surveyed to see if they would be willing to pay a set entrance fee next year. The event could run over two days in the future.
Jenny said: "We could charge a higher price for entry if we did that or apply for grants as a new initative, but it is just one of the options we are looking into."
People will not be allowed to take alcohol on to The Meadows. Anyone who does will have it confiscated and police will be on hand to implement the new rule.
Beer will be available at the bar, run by Bourne Round Table, at a cost of £2.50 a pint. There will also be a can express.
Entry to the event will be monitored and restricted to the Vence Walk entrances at Cattle Market and Bath Row. The event starts at 1pm, with gates opening at midday. The bar will close at 10.30pm with a firework display at 10.40pm.
Today, tomorrow and on Sunday there will be no parking in Bath Row between Kings Mill and the first entrance to The Meadows. Tomorrow Vence Walk footpath across The Meadows will be closed to the public and road access between Castle Dyke, Kings Mill and Bath Row will be closed to non-residents. The pay and display car park in Bath Row will also be closed to the public. Another public footpath, between the first and second meadow, will be shut.
l Festival schedule – page 73