Start of autumn in South Australia is expected to be the hottest in at least a decade

The first days of autumn are tipped to be the hottest in at least a decade as South Australia enters another heatwave, the third of 2019.

The first days of autumn are tipped to be the hottest in at least a decade as South Australia enters another heatwave, the third of 2019.

The Bureau of Meteorology is predicting the hottest start to March since a sizzling late season heatwave in 2008 which lasted 15 days in a row and included six days over 40C.

The current heatwave, which descended on South Australia at the weekend, is forecast to be short by comparison.

Today is expected to reach a top of 37C after it dropped to 25C about 2am this morning. Tuesday should reach 36C and it should be 37C again on Wednesday and Thursday.

The heatwave is expected to reach a peak of 40C on Friday and Saturday, before a cool change arrives on Sunday morning, bringing the possibility of a few spots of rain and a top of 29C.

Bureau senior forecaster Brett Gage said the relatively calm but hot temperatures were a result of weather patterns in the Tasman Sea.

Sophie Prytharch and Jack Grayson, from England, enjoying the Australian sun at Glenelg Beach. Picture: AAP / Morgan Sette

“When you have an intense low system and a high pressure system in the Tasman at the same time we call it a blocking pattern because it stops other weather systems,” Mr Gage said. “So in our case the blocking pattern is pushing weather systems to the south east. Until the blocking pattern weakens we aren’t going to see much of a change.”

The Country Fire Service has declared the Mount Lofty Ranges a total fire ban on Monday with more restrictions likely to be declared as the heatwave continues.

The CFS is also warning against complacency after a man was reported and fined by police for inadvertently starting a fire with a lawnmower on Saturday.

The 38-year-old Jupiter Creek man was using the lawnmower without appropriate safe guards when it ignited a fire which spread through four hectares of grassland.

John Walker and his daughter Alexandra, 6, enjoying the hot weather at Glenelg Beach. Picture: AAP / Morgan Sette

CFS state duty commander Nik Stanley said vegetation throughout the state was dry and at high risk in the event of a fire.

“While mowing, slashing or using a brush cutter you need to have a four metre cleared space around the activity, along with a shovel or rake and a portable water spray in hand,” he said.

“If possible, postpone these activities to when we have milder weather.”

Health Minister Stephen Wade said the heatwave was likely to put pressure on a health system already struggling to cope with ramping.

“This is likely to be a period where there is more pressure on our hospital departments, because often heat can aggravate chronic and complex conditions,” he said.

A cool change is forecast to hit the state by Sunday.

John Walker, 37, and his daughter Alexandra, 6, were enjoying the warm weather at Glenelg on Sunday.

“It’s the best thing about the heatwave, summer is just about done so we are getting to the beach and swimming as much as we can as a family,” Mr Walker said.