"More than half a month's worth of rain fell in Katherine today," a bureau spokeswoman said.

"More than half a month's worth of rain has fallen in Katherine today as storms producing thunder and lightning travelled over Katherine early this morning, dropping 5mm of rain."

The average rainfall for the Katherine area in September is 5-10mm (using Tindal weather station observations).

The highest rainfall recorded across the month of September was 68.2mm in Tindal in 2016.

This morning's rain fell between 3am and 4.30am, dropping 5.2mm over Tindal and 5mm over Katherine Bridge. Maud Creek north of Katherine received 3mm.

More reading: La Nina called by American forecasters.

The storms that brought the rain were part of a large thunderstorm system that is stretching across southern inland Queensland, much of eastern and inland New South Wales and eastern Victoria.

"Remaining cloud from the storms may help keep Katherine from reaching the 40°C forecast for today, but it will be a hot next few days with above average temperatures expected across inland areas including Jabiru and north western parts of the Barkly," the spokeswoman said.

There is a slight chance of a shower or thunderstorms in Katherine tonight or early tomorrow, increasing to a slight to medium chance later in the week as a trough arrives from the south.

*Tindal is a good choice for climate statistics for Katherine. It has had more consistent observations than Katherine in recent years. The rainfall numbers between the two sites are close."

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