There is a small chance a cyclone could develop off the Top End coast, the weather bureau has said.
Forecaster Sally Cutter said a trough was forming and the Top End should expect heavy rain over the next week.
She said the bureau would closely monitor the trough to see if a low developed.
"It looks like it's just, the trough, going to sit along our north coast for most of the week," Ms Cutter said.
"So it looks like it's going to provide a lot of rain across most of those areas, and we do have flood threat advice out."
© ABC 2013
16:28 EDT Hail is caused when raindrops are lifted up into the atmosphere during a thunderstorm and then supercooled by temperatures below freezing, turning them into ice balls.