As a result of the high weekend temperatures, national parks including Mt Canobolas will close and electricity could be cut due to an overloaded grid.

The forecast temperature comes after weeks of hot weather that has seen waiting lists grow for air-conditioning installation and repairs.

The supply of fans and air-conditioners has struggled to keep up with demand at retail outlets.

ThermalAIR refrigeration mechanic Adam McDonald said working on air-conditioning systems in roof spaces where the heat is trapped, was a particular issue.

“If you are doing it in the roof it’s in half hour increments and you keep your fluids up, we make sure you are being safe,” he said.

“You get into a roof and when you start to feel not normal you get out and sit in the shade for a while.

“We are drinking three to four litres of water a day, we bring a couple of one and a half litre water bottles with us and accept drinks from clients.”

ThermalAir Orange general manager Rob Dawson said it’s the busiest it’s been in months with a two to four-week waiting list and air-conditioner sales have increased by 20 per cent but supplying products has become difficult.

“There are low levels of supplies in Sydney with some suppliers unable to give you a due date of arrival because there’s such a large demand nationally,” Mr Dawson said.

“We’ve experienced a lot more breakdowns this year and I think it’s because a lot more people are using their air-conditioners and they are not getting turned off as regularly.”

Weily’s Betta Home Electrical said nine out of 10 customers have been looking for cooling and by mid-afternoon Friday fans were sold-out, there was a “smattering” of air-conditioners and they were waiting for trucks to arrive with new stock.

“We’ve got everything we can get in and it goes within a few hours,” store manager Mark Andrew said.

“All around Australia our suppliers have run out, especially with air-conditioners.

“Because it’s been like this since Christmas we’ve never had this experience.”

He said the duration of the heat as well as humidity caused by moisture from last year’s record breaking rain being trapped in the soil led to more people seeking cooling devices this year.

Since records began at Orange Airport in 1994, the record February temperature stands at 37.9 degrees from February 21, 2004.

However, Weatherzone meteorologist Kim Westcott said the highest recorded temperature was 38.1 degrees on January 12, 2013.

Cooler temperatures are expected next week.