Climate researchers say signs of an early spring are a disturbing reminder of global warming.
Warm winter temperatures have triggered an early outbreak of pests at Sydney's Botanical Gardens, and ibis chicks are already in the hatching phase.
There are also reports that magnolias are blooming a month earlier than usual in the Blue Mountains.
Climate Institute CEO, John Connor, says small seasonal changes are starting to add up.
"What we are seeing is natural cycles being throw into a spin, and we are not quite sure what the exact outcomes might be of this," he said.
"But it's not a good thing to see the natural cycles taken out of order."
Horticulturalist Paul Nicholson says garden pests are becoming an increasing problem.
"One of the things we've had a problem with this year is a particular caterpillar that affects clyvias, which are a big part of our landscape here within the Sydney Gardens but also all around Sydney," he said.
"This year its been active right up until now, when normally it would stop being active around May or June."
A persimmon grower from Camden, Brett Guthrey, says his harvest lasted an extra four weeks.
"It stayed on the tree longer," he said.
"It had more flavour and it was sweeter."
The average temperature was 19.5 degrees in July - 3.2 degrees higher than usual.
© ABC 2013
11:39 EDT El Nino is one extreme of the El Nino-Southern Oscillation (ENSO) phenomena, in which La Nina is its counterpart.