Eastern cities have seen records for consecutive warm days in May but plants could suffer from the 'false spring'

This article is more than 6 years old

This article is more than 6 years old

Autumn leaves aren’t shedding, fruits crops are being fooled into flowering and shops can't sell winter coats as unseasonably warm weather continues to break records across Australia’s south east.

Melbourne has seen nearly a fortnight of temperatures above 20C this month, while Adelaide has also set a new May record experiencing 18 consecutive days above the same mark.

Wednesday was Sydney’s 18th straight day of temperatures higher than 22C – also a record for this month – and unusually high temperatures are set to continue for "months".



Weather-watchers call it a “warm wave”, the result of a blocking system in the Tasman keeping hot weather patterns, which normally migrate eastwards over the continent, trapped over the east coast.



These warm waves, which graduate to “heat waves” in the summer, are becoming more common, according to Karl Braganza of the Bureau of Meteorology. “Going back to the end of 2012, every six weeks we’ve seen a significant heat wave or warm wave affect a part of the country,” he said.



A shift in the baseline temperature associated with climate change means the air being trapped is warmer, too, by about one degree, Braganza said.



While many Australians have welcomed the extended summer, the heat is playing havoc with industries that rely on temperatures falling during Autumn.



“It’s definitely impacting. The takings are considerably down, and we’ve had to cut staff,” said Heather Grieve, owner of Melbourne coat sellers Piccadilly Circus whose tagline is “If it’s chilly, come to Piccadilly”.

“On Saturday, my takings were half of what they were before, and Sunday it was even worse than half,” Grieve said.

Lynda Chambers at the BOM's research centre looks at the impacts of climate variability on Australia's plants and animals, and has received a number of unseasonable observations.



Among them are very late leaf drops in elms and European plane trees across Melbourne, Scarlet Honeyeaters exhibiting nesting behaviour, and nightly visits by lesser long-eared bats long after they should have become scarce.



“False springs” are also being reported in some fruit crops. “With the warm weather [some fruit trees] can start to move, so they might start to swell, or in some cases flower,” Rebecca Darbyshire, a research fellow at the University of Melbourne’s school of land and environment, said.



“Here in Tatura [in Victoria’s Goulburn Valley], we did notice some cherry trees seem to have moved a bit, so their buds are starting to grow. What happens if they do burst early, then they’ll bit hit by the cold weather and they’ll die,” she said.



Braganza said there was no indication the mercury would drop in the next week, and that above average temperatures were “very likely” to continue for the next few months.

