South Australia is in the grips of its second heatwave in as many weeks while firefighters in NSW are anticipating the bushfire danger to ramp up.

Adelaide will be slammed by another four days of extreme heat while regional centres can expect about 45C after the state experienced a run of 40C days last week.

Bureau of Meteorology state manager John Nairn says the sustained very hot conditions are unusual for December but more could be on the way this summer.

Mr Nairn says such heatwaves are more generally associated with January and February.

“We’re actually building into the heatwave season, rather than peaking,” he said.

The second stretch of scorching days also has the South Australian Ambulance Service bracing for a spike in heat-related calls.

Thirsty koala approaches cyclist for drink as temperatures reach 40 degrees – SA heatwave video ❤️❤️ https://t.co/He7zphdrR2

— Trisha (@LushTrisha80) December 28, 2019

Since the beginning of last week’s heatwave, paramedics have responded to 575 heat-related incidents, with 266 people taken to hospital.

Extra crews have been rostered over the next four days to cope with an increase in calls.

Adelaide is forecast to have a top temperature of 38C on both Saturday and Sunday before hitting 40C on Monday ahead of a cool change later in the day.

But in regional areas, the mercury will go higher with many centres forecast to have tops around 45C over the coming days.

Canberra is forecast to hit a Saturday high of 38C while the mercury will rise to 35C in Batemans Bay, 41C in Griffith and 41C in Gundagai.

Sydney will experience a comfortable 29C day but temperatures across western Sydney and on the city’s fringe are likely to top 35C.

Temperatures are expected to peak on Tuesday, with New Year’s Eve forecasts of more than 40C across western Sydney and in regional NSW.

The RSPCA called on organisers to postpone one of the biggest night rodeos in South Australia, Carrieton Rodeo, due to heat.

“In the forecast conditions, it’s likely some animals will suffer heat stress but it will be difficult to verify how many have suffered or to what extent,” RSPCA’s Rebekah Eyers said.

“To demonstrate that animal welfare is a priority, we had hoped Australian Professional Rodeo Association and event organisers would follow the lead of other organisations using animals for entertainment, and cancel or reschedule the event.”

Club president Daniel Williams said the 67th annual rodeo was “absolutely going ahead” with up to 3000 people to attend and pump money into the drought-stricken town.

NSW

The bushfire danger is ramping back up across NSW, with higher temperatures prompting total fire bans in three regions.

Fires will be banned in the open in the southern ranges, southern slopes and Monaro alpine areas on Saturday, with daytime temperatures forecast to sit well above average across much of the state.

Thunderstorms are also possible across the state’s south and west.

Very high fire danger is forecast for nine NSW regions and the ACT.

A warm and windy weekend is on the way. Total fire bans are now in place for the Monaro Alpine, Southern Ranges and Southern Slopes. Good idea to get outside this morning and prepare your property before it gets to hot. #NSWRFShttps://t.co/D5BrP9dJqH

— NSW RFS (@NSWRFS) December 27, 2019

The Bureau of Meteorology expects the fire danger to continue escalating into next week, with increasing heat and dry winds.

Temperatures are expected to peak on Tuesday, with New Year’s Eve forecasts of more than 40C across western Sydney and in regional NSW.

The rising temperatures come after firefighters spent the past five days striving to contain large and complex bushfires before conditions worsen.

After a devastating end to last week, with two firefighters killed and as many as 1000 NSW houses destroyed, firefighters have taken advantage of milder conditions to strengthen containment lines.

Almost 1300 were in the field on Friday as 70 bush and grass fires continued to burn, with more than 30 yet to be contained.

RFS Commissioner Shane Fitzsimmons said firefighters had completed challenging work in areas such as the Blue Mountains and south coast, backburning and establishing containment lines with hand tools and machinery.

Mr Fitzsimmons said the RFS was not expecting the earlier catastrophic conditions to return, but firefighters and communities would be challenged.

Blue Mountains City Council mayor Mark Greenhill told AAP this year’s extended bushfire season meant locals were living with immense stress.

The area continues to be affected by the Ruined Castle and Grose Valley fires, which spread from the Gospers Mountain mega-blaze to the north.

The Green Wattle Creek fire to the south may also pose a threat in the future, Mr Greenhill said, adding the community was “far from out of the woods”.

“For the whole community this is a very stressful, long endurance episode for them; it just goes on and on,” he said on Friday.

NSW Emergency Services Minister David Elliott, meanwhile, has gone on a family holiday overseas but says he’ll continue to receive bi-daily RFS updates.

His frontbench colleague Anthony Roberts has stepped into the role from Friday.