It's baking at the Big Day Out as the nation faces a roasting

IF you're planning a barbecue or a trip to the beach today, the good news is the sun is expected to be shining across the country.

IF you're planning a barbecue or a trip to the beach today, the good news is the sun is expected to be shining across the country.

The bad news is that in many places it's going to be so hot that a day in the great outdoors might not be appealing. Temperatures in parts of Sydney are forecast to exceed 43C, while the mercury in Canberra and Perth is likely to reach the high 30s.

But the heat is unlikely to deter thousands of music lovers from attending the second of two Big Day Out concerts in Sydney.

Yesterday, at the first BDO gig at Homebush, in Sydney's west, hundreds of people were treated for dehydration and intoxication. While the heat was responsible for many of the health problems, one 20-year-old woman was taken to hospital with suspected spinal injuries. More than 30 people were arrested inside the concert grounds for possession of ecstasy and cannabis, police said.

The temperature at Homebush reached 40.1C, and it is forecast to be even hotter today, prompting police to issue a warning that the combination of heat and alcohol or drug use could prove "deadly".

David Jones, head of climate analysis at the Australian Bureau of Meteorology, said the hot weather experienced in NSW and Victoria in recent days was the result of a hot air system that had drifted across the continent from the west coast.

So far this summer, daily temperatures across the country have been slightly above average.

"There have been some long stretches of hot weather this summer, particularly in southwest Western Australia and South Australia," Dr Jones said. "Across Australia, maximum daily temperatures have been, on average, about 0.5 degrees higher in December and January compared with the same time last year."

Having sweltered through eight consecutive days of temperatures above 35C in November, Adelaide is set to endure another hot week, with the mercury expected to hover in the mid-to-high 30s for a few days from Monday.

Canberra will also face scorching heat in coming days, with the maximum daily temperature not expected to drop below 30C until Thursday.

Additional reporting; Pia Akerman