South Australians have been warned to prepare for thunderstorm asthma over the Christmas period but they will at least get relief from the sweltering heat sooner than expected.
Adelaide is expected to be the hottest city in the world on Christmas Day at 40C but the weather bureau has knocked their prediction for Boxing Day down from an earlier forecast of 40C to a far milder 29C.
While the heat won't be as oppressive as first thought, the thunderstorms expected to hit on or after Monday may bring a different kind of danger.
The National Asthma Council of Australia says the storms could trigger asthma attacks not only for people with asthma but for anyone who experiences serious hay fever.
"As we have seen with the recent events in Melbourne, any serious asthma attack can be life-threatening and have tragic consequences," the council's chairman Dr Jonathan Burdon said in a statement on Friday.
He advised South Australians to act quickly if they experience wheezing or shortness of breath and for asthma sufferers to keep a puffer on them over the coming days.
Thunderstorm asthma can occur when storms strike on hot and windy days during times of high pollen.
In these conditions, pollen grains absorb moisture and burst into tiny allergenic particles that can trigger a serious asthma attack if inhaled, even in those who haven't had one before.
Eight people died and more than 8500 were hospitalised when the world's worst ever thunderstorm asthma event hit Melbourne in November.
The downgraded forecast in SA flows from the weather systems at play in Australia's north-west, including Cyclone Yvette over the Indian Ocean and an intense low over Western Australia.
"Our temperature has been dependent on the exact movement of those low pressure systems," the Bureau of Meteorology's senior forecast Tina Donaldson said.
"It's not uncommon to get big changes in the forecast when you've got such a variable system at play."
She said Adelaide and much of SA will be cooled by southerly winds moving through on Boxing Day.
Christmas Eve (37C) and Christmas Day are likely to carry the highest bushfire risk because of the scorching heat.
The state government said it will do all it can to keep the lights on for the occasion, with the number of businesses closed for Christmas likely to lower the chance of blackouts.
