Many parts of NSW had hovered around 45 degrees at lunchtime on Friday as a fiery air mass from inland Australia moved over the state, pushing the mercury well above the forecast maximum. Beating down ... Sydney registered a record temperature this afternoon. Credit:Andy Zakeli In Sydney, the original forecast was that the temperature would reach a maximum of 39 degrees in the city. But by 12.30pm the mercury had already hit a stifling 43.3 degrees at Observatory Hill, climbing to 45 degrees at 1.43pm, 45.2 degrees at 1.58pm, 45.3 degrees at 2.27pm and 45.7 degrees at 2.54pm. The city's temperature dropped to 33.9 degrees at 5.04pm. In the west, Penrith hit 46.5 degrees at 2.16pm. Sydney Airport hit 46.4 degrees at 2.32pm. Weatherzone meteorologist Ben Domensino said this was the second day this month the city had sweated through temperatures over 40 degrees. That had happened only four times in January in the past 107 years.

"Sydneysiders may find this type of heat unusual," he said. "Last summer only saw the mercury reach a top of 33.4 degrees, and [the city] recorded just two days over 30. On average, the city typically reaches 40 degrees once every three summers, although this year has seen an unusually hot start. "Reduced cloud cover over central and western Australia during the past few weeks has allowed a very hot air mass to build. This heat has periodically made its way towards the nation's coast due to the passage of low pressure troughs across the nation's south." Transport problems The record heat across the city triggered multiple failures on Sydney's train system as steel wires buckled and a hose used to run a key signalling system melted.

There have been at least three equipment failures on the CityRail network on Thursday afternoon, triggering widespread delays across the city as train commuters swelter in air-conditioned and non-airconditioned carriages. At Dora Creek, on the Central Coast, the heat caused an overhead wire to buckle onto a train at about 1.30pm. About 250 passengers were trapped on the train for about half an hour, until CityRail could organise another service for them to switch to. At Strathfield about 4pm, where the signalling system is powered by compressed air, one of the hoses melted. This caused the entire signalling system, which controls the movement of trains from one track to another, to shut down for about 35 minutes. RailCorp’s chief operating officer, Tony Eid, said the problem had now been repaired but there were delays of about 40 minutes across the network. Mr Eid said the Illawarra and Eastern Suburbs line was the only part of the city’s train system to be unaffected. Earlier, there were delays around Redfern after an overhead wire sagged onto a stationary train in a siding near Eveleigh. This triggered the automatic closure of an overhead power line near Redfern for about 40 minutes from 2pm. Trains on multiple lines have been delayed since.

Mr Eid said wires tended to buckle on areas where RailCorp had not yet installed weights to maintain their height in extreme heat. He said no tracks had buckled on the system. Monorail fire The heat also shut down Sydney’s monorail, after sparks starting flying off one of the trains started a grass fire underneath. An employee of Veolia Transport, which operates the monorail, said all passengers were now off the monorail train and the line was closed as of 5.40pm. "There was no train on fire, there was a grass fire," said the employee, who gave her name as Renata.

A picture posted on Twitter shows the fire was in Ultimo, next to Darling Drive. The Veolia employee said the fire department had extinguished the grass fire, which was probably caused by a "technical problem" on the monorail vehicle. The line will be closed down for good in the middle of the year. Firefighters battle bushfire The heat was expected to peak in the low 40s around Coonabarabran, where firefighters are battling a 46,000-hectare bushfire that has destroyed 51 properties since it ignited last weekend. A total fire ban has been declared for Friday.

At midday on Friday the fire was burning in the Bugaldie area, one kilometre south of Bugaldie village, and eight kilometres west of Coonabarabran. The Newell Highway has been closed in both directions near Gowang between Gilgandra and Mendooran Road in Warkton. An emergency alert telephone message has been sent to residents in the area, and residents have been advised to follow their bushfire survival plans and monitor conditions. "The fire is burning close to rural properties in the Bingie Grumble Road, Cenncruich Road, O'Connors Road, Gowang Road and Tannabah Road areas. People in these areas must remain vigilant and stay up to date with the changing fire conditions," the Rural Fire Service said in a statement. Weatherzone meteorologist Ben McBurney said the heat was likely to linger over that region into Saturday.

"It's not going to be as hot on Saturday, probably in the high 30s, but still not very useful for the fires over there," he said. Loading - with Jacob Saulwick Weatherzone.com.au is owned by Fairfax Media, publisher of this website.