Rain or shine for Big Day Out?

The weather looks set to behave for the Big Day Out in Auckland on Friday, although the morning before the concert could be a little damp.

The country's biggest concert is being held at Western Springs Stadium, with the first performance due to start at noon and the last to finish at 11pm.

MetService communications meteorologist John Law said a weak system moving up from the south would bring a few showers in the morning.

"For the afternoon it should improve with cloud breaking up and some nice spells of sunshine," he said.

A maximum afternoon temperature of about 23 degrees Celsius was likely, although a southwesterly breeze pushing through could make it feel a bit cooler.

The weekend weather was expected to be decent over much of the country, but things could get more interesting early next week with a tropical cyclone possibly forming over the Coral Sea, Law said.

"Conditions are looking favourable for a fairly active system to form," he said.

"It does look like it heads towards us, towards the start of next week."

The impact that would have on New Zealand was far from certain.

The MetService five-day rain forecast today showed an area of intense rain heading south.

By 1am on Monday the centre of the system is shown over the sea east of southern Queensland and northwest of New Zealand.