Sydney swelters through hottest January night in history

Sydney residents have tossed and turned through a record-breaking hot night.

Among the all-time high temperatures recorded were Observatory Hill at 26.4C, Penrith at 28.6C, and Camden at 27.1C, the Bureau of Meteorology reported.

Richmond and Bankstown also sizzled at a sleepless 28.2C and 26.2C respectively.

Yesterday thousands of people across Sydney's west lost power after temperatures climbed to around 45C in the day, the hot, dry and windy conditions prompting the RFS to issue total fire bans across most of the state.

Relief from the heatwave is forecast to arrive tomorrow, with the mercury dropping to a maximum of 26 degrees in the CBD with scattered showers, according to BoM.

Temperatures for the rest of the week will remain in the high 20s to low 30s.