Rainfall records have tumbled in the Northern Territory after a weekend deluge brought heavy falls to parts of the Top End.

With more than a week to go until the month ends, several regions have already broken September monthly records, some of which have stood for decades.

Katherine recorded 104.6 millimetres in the 24 hours to 9:00am this morning, well above the previous September 24-hour rainfall record of 90.9mm set in 1895.

During the same period, Mainoru Station, about 200 kilometres north-east of Katherine, recorded 168.2mm, the third highest 24-hour rainfall ever recorded in the Northern Territory in September.

'A pretty massive event'

Greg Browning from the Bureau of Meteorology said more rain was expected to fall in coming weeks, due mainly to the impact of a strongly negative Indian Ocean dipole that affected sea surface temperatures.

"A lot of the single-day [rainfall] totals are beating the old monthly records," Mr Browning said.

"It is a pretty massive event."

As well as the Top End, there have also been heavy falls in southern regions of the NT, with 23.4mm falling in Alice Springs, nearly three times the monthly average of 8.1mm.

But Mr Browning said the heavy rain during the build up did not necessarily mean Territorians should brace for a wetter than usual wet season.

He said the Indian Ocean dipole affected build-up rain, but wet season rain would be dependent on whether a La Nina weather pattern occurred.

He said at the moment there was not a strong La Nina signal, and an average wet season was forecast.