It’s a hot day at Sydney’s Bondi Beach. But even hotter in the city’s west. Picture: John Grainger

At 1.30pm temperatures had reached 34.2C at the CBD’s Observatory Hill and at 2.30pm a scorching 36.6C in Penrith in the city’s west.

Wednesday’s temperatures are more than 10 degrees above average for this time of year and have easily surpassed the previous record April high of 33C recorded in 1986.

The Bureau of Meteorology (BoM) has warned temperatures could continue to rise as the afternoon wears on.

But don’t tell Melburnians who have spent Wednesday shivering through a chilly Autumn day struggling to even get into the mid teens.

Forecasters had been predicting a high of 29C in the centre of Sydney for Wednesday but the mercury had surpassed that figure by 10am.

“We thought there would be a bit of a sea breeze around the coast today to bring temperatures down,” Miranda Langston, a BoM forecaster told news.com.au.

“It hasn’t happened, so as a result we’ve we got high temperatures of 34 degrees in the city. It’s pretty crazy.”

Just days ago, 94mm of rain fell on Sydney.

Canberra is also feeling the heat with an expected high of 31C. Brisbane is hovering around 30C but Perth and Adelaide are only expected to get into the early twenties on Wednesday.

A total fire ban is in place in the NSW lower Central West plains.

But enjoy it while you can because, similar to how the night is always darkest ahead of the dawn, so the heat is often hottest ahead of a cold change.

“There is a pretty vigorous cold front and southerly change moving through the South Coast, currently around Moruya, and that’s expected to reach Sydney around midnight,” said Ms Langston.

The cold front started it’s journey southwest of Perth, off the Western Australian coast, on Monday before heading over the Great Australian Bight and then into SA and Victoria.

In Melbourne, where the change has already made its presence felt, the mercury struggled to reach 14C on Wednesday.

Thursday is likely to see Sydney temperatures at least 10 degrees cooler, between 22 and 24C, just a point or two above the average for April.

Heat from the continent’s red centre is spilling down to the eastern coast. Picture: BoM.Source:Supplied

Nevertheless, one-off rises in temperature could continue throughout the month as the current El Niño has one last hurrah.

The El Niño, which was declared in early May 2015, has developed into the most significant and largest for nearly two decades, ranking alongside those in 1997-98 and 1982-83.

The phenomenon is caused by warmer sea temperatures in the Pacific sucking warm, moist air over North America while leaving Australia hot and dry.

The current conditions chimes with the BoM’s climate outlook up to June which predicts a weakening El Niño, bringing above average rainfall for the southern parts of the continent but not immediately.

However, the full effects of the El Niño dropping off are not expected until midwinter, meaning April is likely to remain dry with no guarantee of much rain or typical autumnal conditions, predicts the BoM.