As the UK braced itself for heavy snowfalls, Sydney was experiencing its hottest day on record, with temperatures reaching almost 46°C.

A temperature of 45.8°C was recorded at Observatory Hill in the city just before 3pm local time.

Some areas in the wider Sydney region were even hotter, with the town of Penrith, to the west, registering a temperature of 46.5°C, the BBC reported.

The previous recorded high in Sydney was in January 1939, when the thermometer topped 45.3°C at Observatory Hill.

Officials warned people in Sydney to take care, avoid strenuous activity and stay out of the sun.

The heat damaged wiring to urban railway lines, bringing delays to much of the network.

Firefighters were still battling dozens of wildfires sparked by the intense heat in New South Wales and Victoria.

Prime minister Julia Gillard advised people to “take the appropriate precautions to stay safe and monitor information from local emergency services as they work to protect lives and property”, the AFP news agency reported.