Thousands of visitors are expected to converge on the town to view the parade and enjoy the entertainment in Pioneer Park before and afterwards.
Six floats made of thousands of paper flowers are entered in the parade, which will also feature big rigs, vintage cars, pipe bands, marching groups, brass bands, community groups and a host of entertainers.
The procession begins with a truck display at 11am, followed at noon by the floats, walking groups, bands and other entertainers.
Last year, a fierce storm delayed the start of the parade by an hour but festival chairman Steve Battrick was confident the weather would be warmer this year.
"All weather forecasts are predicting a clear day and it will improve all day. Sunday's forecast is equally nice," Mr Battrick said.
"Obviously, you get a bit anxious and realise the weather does make a difference, but it would go ahead rain, hail or shine."
Despite the cold weather last year, people still seemed to enjoy the day, he said.
Alexandra has taken on a festive air, with new street banners and Chinese lanterns decorating the park for the Contact Energy-sponsored festival.
Although only six floats had entered in the procession, it would still be "a mass of excitement and colour", Mr Battrick said.
The activities in the park afterwards include a pipe band competition, the crowning of the festival queen, children's entertainment and performances by the Wellington Ukelele Orchestra.
The festival programme includes a garden tour tomorrow and Monday with cooking demonstrations by chef Al Brown, of Logan Brown restaurant in Wellington, who also features on the television programme Hunger for the Wild.
Tomorrow's activities also include drag racing at the Alexandra airport.
The festival concludes on October 3, with the WoolOn creative design awards.
