Flash flooding in Byron Bay amid heavy rain, storms

Byron Bay has been hit with flash flooding with several streets in the middle of the coastal holiday town inundated as the region was hit with heavy rain this afternoon.

Video posted to Instagram shows workers wading through calf-height water on the corner of Byron and Jonson streets, outside Byron Corner Store, beside parked cars with water halfway up the wheels.

Intense thunderstorms have dropped 75mm of rain on the Northern Rivers of New South Wales in just an hour, Weatherzone reports.

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Ballina copped 86mm in the three hours to 12.15pm AEDT.

The Bureau of Meteorology issued a severe thunderstorm warning for heavy rainfall, just after 1pm AEDT which remains in place.

A similar warning is also in place over the border in Queensland with heavy rainfall forecast for parts of south east Queenland including Ipswich, Logan, Brisbane City and Moreton Bay.

Rain set to continue in wet start to autumn

More rain is forecast to fall across large parts of the country this month, continuing a wet start to autumn that has led to widespread flooding across multiple states.

A series of low-pressure troughs and low-pressure systems dumped heavy rainfall over areas already saturated by summer rain, causing widespread flooding in NSW, Victoria and South Australia over the past few weeks.

Flood disasters are ongoing in Queensland, where two Chinese backpackers headed west to find fruit picking work were found dead in their car and the Northern Territory, which is experiencing its worst flooding in decades.

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Weatherzone's Ben Domensino said the wet and soggy forecast was thanks to a phenomenon called the Madden-Julian Oscillation (MJO).

Domensino described an MJO as "a pulse of increased rain and storm activity that moves around the world near the equator roughly every 30 to 60 days".

He said it increased the likelihood of more wet weather, particularly across northern and central Australia, in the second half of March and possibly into early April.

The Bureau of Meteorology's long-range forecast for autumn also anticipates above-average rainfall and a heightened flood risk for much of the tropical north of the country for the rest of the month.

From April through to June, the forecast is for below average rainfall for most of the country, excluding the far north, heading into the dry season starting in May.

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