The rain is going to become heavier throughout the day with a severe weather warning issued for the Northern Rivers by the Bureau of Meteorology.
A strong upper trough is moving slowly eastward from central Australia towards the east coast into Thursday.
On top of that a surface trough in south-east Queensland is forecast to slowly drift south towards north-east NSW and deepen in response to this approaching upper weather system.
The surface trough will bring heavy to intense rainfall from later today and into Thursday.
This could lead to flash flooding north of Ballina later today and into Thursday.
The six-hourly rainfall totals could hit 150-200 mm.
Locations likely to be affected include Kyogle, Tweed Heads, Murwillumbah, Mullumbimby, Byron Bay and Brunswick Heads.
The next weather update from the Bureau of Meteorology is at 11am.
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