SPRING starts today, with more than a tinge of summer already in the air. The Bureau of Meteorology predicts a relatively warm, dry end to the year, with average spring temperatures creeping closer to those experienced in summer 30 years ago.
The rain-bringing La Nina weather cycle that haunted the last two Australian summers is gone, and its hotter twin El Nino is gathering pace.
''The last couple of years have been La Nina years, and those tend to bring above average rainfall and cool conditions,'' said a climatologist with the Bureau of Meteorology, Acacia Pepler. ''Now, we're in a neutral year, trending towards El Nino, and we're expecting average to warmer weather.''
The weather cycles are not completely understood, but meteorologists have been able to accurately track and predict extended dry and wet spells by measuring sea surface temperatures in the Pacific Ocean, between Darwin and Tahiti. Warmer water creates higher air pressure over the ocean, causing drier conditions over much of eastern Australia.
Sydney tends to be buffered from the most extreme El Nino-La Nina impacts, which have traditionally fallen west of the dividing range, but the trend towards El Nino means this year's spring temperatures will probably be higher than normal in the daytime.
''In the records since 1859, the average spring temperature at Observatory Hill is 21.9 degrees, but keep in mind that Observatory Hill has been warming up over the years,'' Ms Pepler said.
Daytime averages of about 23 degrees - quite balmy compared to the past two years - are expected for Sydney's spring this year. The bureau's climate models say there is a 60 to 70 per cent chance that temperatures for most of NSW will be above average.
Warmer, drier air means the risk of bushfires is also rising, and the NSW government announced this week that hazard reduction burns will take place in about 6000 hectares of bushland in and around the city. It means parts of Sydney could be shrouded in a smoky haze for the next few days.
Today, a hazard reduction burn in Royal National Park has been postponed due to likely high winds but others will proceed.
''The crews are taking advantage of the ideal spring conditions after a string of extremely wet seasons, including last years' record winter rainfall and an unusually wet, cold autumn,'' said the Environment Minister, Robyn Parker. ''This is a window of opportunity to carry out burns scheduled for last year and postponed because of rain, as well as continuing with operations scheduled for this spring.'' About $62 million had been allocated to an expanded hazard reduction program, she said.
This weekend, there will be hazard reduction burns in Ku-Ring-Gai Chase National Park, the Blue Mountains National Park, Berowra and Palm Beach, while there will be a controlled burn at Macquarie Park, next to the Lane Cover River, on Monday.
About 2400 hectares of national parks and reserves have been burned since July 1, in 10 separate controlled burns, the Office of Environment and Heritage said, with another 12 due to take place this week.
Altogether, 30,000 hectares will be burned for safety reasons by the end of November, in 70 separate hazard reduction operations.