Sydney's Big Day Out and Tamworth's Country Music Festival attracted thousands of visitors from around NSW, while the Illawarra Folk Festival in Bulli held its own despite record heat.

Illawarra fans of the Killers, Red Hot Chilli Peppers and Yeah Yeah Yeahs arrived at North Wollongong train station early yesterday ready to head to Sydney Showground for a very hot, very big day out.

As temperatures soared towards 40 degrees at 11am, guys with muscle tops already off and tucked into low-slung shorts joined girls wearing midriffs and cut-offs.

At a bus stop near the station, 50 friends piled on to a giant blue and yellow school bus, most carrying cases of cheap mixed drinks and bags of ice, some already halfway through their first beer.

"Wish it was a bit hotter," one young man remarked as he stepped on board.

Yesterday was the ninth Big Day Out for the rowdy crew's ringleader Nathan McBriarty, 25, making him well-prepared for a day of scorching hot concrete, sweaty bodies and red hot bands.

"It's always a good line up, heaps of fun - it's the best summer festival and it's always the hottest day on earth," he said.

At Bulli Showground, Illawarra Folk Festival crowds sought a prime position at one of the small air-conditioned stages or bars, taking advantage of large industrial fans provided by organisers.

Marketing and media director Peter O'Neill said numbers remained high even though the festival grounds looked quiet, as people refused to budge from the shade.

"There's a few air conditioned venues where it doesn't matter what sort of music is playing ," he said.

"The ice cream guy is also very popular."

He said not everyone was affected by the heat.

"I've just been photographing some people, including these girls at a blues concert jumping up and down," Mr O'Neill said.

"I don't know where they get their energy because everyone else is just exhausted."