As Ireland shivers, Sydney recorded the record today, eclipsing the previous high of 45.3C on January 14, 1939, according to the Bureau of Meteorology.
"Quite simply, Sydney is melting today," said Corey Watts, regional projects manager at The Climate Institute.
"This kind of weather cannot be taken lightly. These heat waves can have serious impacts on human health and wellbeing."
Wildfires posed a threat to towns in Australia's Victoria state. More than 80 fires are still ablaze in New South Wales, where about 50 homes were destroyed last week.