Authorities need to find accommodation for about 300 people whose homes are badly damaged.
The livestream began at 6pm on Wednesday.
Scheduled buses will accept train tickets.
It comes just days after a state of emergency was declared in Buller and Marlborough.
The May floods cost hundreds of thousands of dollars and hours of clean-up and the latest rain has done it again.
The mayor is worried hundreds of houses may need to be demolished.
The storm comes as the Caribbean's island nations are already struggling with the economic impact of the coronavirus pandemic.
Canterbury farmers who are still cleaning up after the floods earlier this month are being offered $3500.
The thunderstorms are due to a very humid and unstable northwest airstream which lies over the North Island.