The Bureau of Meteorology has forecast rainfall between 30mm and 45mm for Lismore over the next two days as a trough makes its way across the interior.

As I write this weather update, it is clear blue skies with the temperature climbing to 33 degrees, however, conditions will change later this afternoon.

Helen Kirkup from The Bureau told the Lismore App that today's scenario is perfect for "daytime convection activity".

This is where the earth's surface heats up and the hot air rises to form cumulus clouds, which in the Northern Rivers with our humid weather, will lead to thunderstorm activity.

(The trough scenario at 10am today)

(The trough situation at 10pm tonight as it moves eastward)

The trough will reach the ranges first so Tenterfield and Tabulam before moving towards Casino and Kyogle then drift towards the coast to Lismore.

Helen said the rainfall will be heavier today for western towns which could see between 20 and 25mm while Lismore can expect 10-15mm.

The Bureau is "on the lookout for severe thunderstorms" but that won't become clear until later this afternoon. "There could be heavy rainfall, damaging winds and light hail," Helen added.

The good news is the weather should clear by Friday leaving cooler and mostly fine conditions for the weekend.