Some of the top bands will go on to compete at the World Pipe Band Championships in Glasgow.
Nally said he was keeping his fingers crossed for good weather.
"If it rains we get wet. It is not an option to play inside, we have to be outside."
He said it had been left to each band to organise where they would practise, and a lot would "tune-up" at their motels or in parks.
"We hope that the people of Rotorua can be tolerant. This event has not been here for 20 years."
Nally hoped residents supported bands at tomorrow's competition at the Rotorua International Stadium, or on Saturday at the public parade in the centre city.
Willy Clark is one of four current members of the Rotorua Highland Pipe Band who also played in the band in the 1998 championships.
The 65-year-old started drumming before he was 15, so he realised while speaking to the Rotorua Daily Post that he'd been playing in pipe bands for more than 50 years.
He said there were all sorts of things that kept him involved.
"I enjoy the music, but we do a lot of tutoring too. It is really good to see the young ones come through and progress."
Clark said the last time the Rotorua band won a grade at the national competition was in 2000 at Masterton.
He said he was "quietly hopeful" for 2018.
"We have been doing well this year in the build-up competitions in the North Island but you never know what's going to come up from the south."
Royal NZ Pipe Bands' Association National Championships 2018
- Rotorua International Stadium on Friday from 9am and Saturday from 12pm
- Pipe band competitions, food, stalls, and bar.
- Street march and massed band display on Saturday. 9am start outside Rotorua Primary School.
- Stadium entry $10 per day, under-12s free.
- Road closures: Saturday8am to noon, Rangiuru St (from Whakaue St to Arawa St), Arawa St (from Hospital Entrance to Tutanekai St) and Amohia St (from Arawa St to Haupapa St).
