On Sunday the Penrith observation station reached its highest ever temperature - and, unofficially for the time being, greater Sydney's second highest ever - of 47.3 degrees just after 3.35pm. Penrith residents seeking refuge in the Nepean River during scorching weather of 47.3 degrees on Sunday. Credit:Dean Sewell The city reached a maximum temperature of 43.4 degrees at Observatory Hill, its hottest day in five years. The last time the mercury rose so high in the CBD was in 2013 when Sydney reached 45.8 degrees on January 18, the hottest inner-Sydney day on record. On Sunday, the city was originally forecast to hit 40 degrees, but shot past that before midday.

A cool sea breeze dropped the CBD temperature just before 1.30pm with strong winds helping to push the temperature below 33 degrees by 2pm. That breeze is expected to move west and cool areas around Penrith and Richmond in the late afternoon. Families cool off at Blaxland Riverside Park in Parramatta as the mercury reaches into the 40s on Sydney's second hottest ever day. Credit:Brook Mitchell There is a slight chance of a thunderstorm for Sydney too although no weather warnings have been issued as yet. As temperatures soared across the state, thousands of people were left without power, according to electricity provider Ausgrid. Fans were left high, dry and hot at the Sydney International as organisers ordered players off the court due to extreme heat. Credit:AAP

Power outages across the NSW Central Coast affected more than 4000 properties, while almost 3000 properties were left without power throughout Sydney. An Ausgrid spokeswoman said while additional load on the network from the high temperatures had contributed to some of the outages, there were several other factors at play. The spokeswoman said technicians were working to restore power to the affected areas. At the SCG, where day four of the fifth Test is currently being played, one record was likely broken.

According to Blair Trewin, senior climatologist at the Bureau of Meteorology, the previous hottest Ashes Test day appears to be a 43.1 degree day during the Adelaide Test between Australia and England back in 1908. The SCG is about midway between Observatory Hill and Sydney Airport. The former has already reached 43.4 degrees and the latter 43.7 degrees. The Sydney International tennis tournament organisers forced players off the court at 10am when temperatures courtside exceeded 40 degrees. It was a relatively warm start to the day even at dawn as the mercury failed to dip below 22 in Sydney overnight. Many parts of the city raced above 30 degrees early in the morning.

Penrith was sitting at 30.4 and Campbelltown was recording a temperature of 31.1 degrees at 9am. The city had reached 29.8 at the same time, rising above 30 degrees just 10 minutes later. The hot weather, combined with strong winds, means there is a chance for bushfires to spread out of control. The Rural Fire Service has issued a total fire ban for the Greater Sydney and Hunter Regions, with Sydney being given a severe fire rating. NSW Rural Fire Service Deputy Commissioner Rob Rogers said that smokers needed to be particularly aware on days with total fire bans.

"One of the common things we see people do is throw cigarette butts down," he said. "People should understand that the fine is around $1,300 if we catch you throwing a lit cigarette in a total fire ban." The NSW Office of Environment and Heritage has issued an Air Quality Forecast alert of poor, with ozone levels higher than normal. This means those with respiratory problems such as asthma will need to be extra cautious during the hot weather and keep their reliever medication nearby.