I'm always skeptical of an early or late spring, or of something flowering particularly early or late. We get a bit misty eyed about the seasons. I've spoken elsewhere about my view that spring in Sydney starts in late July or early August - that's when the first flush of spring flowers seem to arrive in the local bush and when our gardens start to bloom. But that's in a typical year, and there isn't really such a thing. The climate each year has an impact on when plants do things like flower. Day length is important, and provides the background settings, but extra rain or warm days also have an impact on most plants. So every year flowering times move around, even though I would argue they seldom conform to the system of four seasons we have inherited from Europe.
So this year the question was why are Jacarandas (a native of South America) flowering so late? They were at their peak last week, the middle of November. I looked back on some notes I made in 2003 (for a radio chat), and it was 4 November when New South Wales was breaking into Jacaranda flower. So not a dramatic tardiness this year. But it seems that in the last couple of years they have actually been a little early, which has meant that this year the feel late. Warm Septembers and Octobers have brought them into flower in mid-October. This year's winter (apparently due to La Nina) has been cooler and wetter, and the Jacarandas are back to their November flowering.
I have been told it is a particularly spectacular year due to the above average winter rainfall, but then in 2003 I noted how spectacular they were due to the particularly dry summer proceeding (stressed plants often flower wonderfully in their attempt to reproduce and set seed - a sense of impending death).
It's always the way with plant flowering. Good and bad years, early and late blooming - so many explanations. The reality is probably quite complex and each species is no doubt responding to different cues. But I would note there is no reason to expect plants, particularly our local native plants, to respond to the quaint European constraints of spring, summer, autumn and winter.