It'll be a scorcher this Wednesday right across the Sydney basin, with coastal suburbs heading for the mid-30s and the outer west likely to give the 40-degree mark a serious nudge under blustery northwesterly winds.

Sydney is yet to experience any heat extremes yet this year. In descending order, here are the highest temperatures recorded in each Australian capital city (at the main weather station) for the first three weeks of 2025:

• Perth 43.6°C on Jan 20
• Adelaide (West Terrace/ngayirdapira) 38.7°C on Jan 19
• Melbourne (Olympic Park) 38.0°C on Jan 5
• Brisbane 37.4°C on Jan 16
• Canberra 36.4°C on Jan 5
• Darwin 34.3°C on Jan 12
• Sydney (Observatory Hill) 31.7°C on Jan 6
• Hobart 31.5°C on Jan 11 

As you can see, Sydney (based on data at the Observatory Hill weather station on the fringe of the CBD) is the mainland capital with the lowest max temp to date this year.

But that looks set to change this Wednesday, with the city heading for a top of 35°C in what will be a relatively brief burst of heat before an afternoon southerly change roars through, dropping temperatures by around 10 degrees in a short period of time.

The combined satellite and radar loop below shows an influx of cooler air making its way northwards to Victoria with the passage of a cold front south of the mainland.

Image: Cooler air pushing onto Tasmania and the southeast mainland on the morning of Wednesday, January 22, 2025.

Melbourne's Tuesday maximum of 28.3°C actually occurred in the morning before the cool air arrived not long after lunchtime.

That cool air has now enveloped all of Victoria, and will wrap around the SE tip of the mainland and surge as far north as the NSW Mid North Coast by Thursday, arriving in Sydney around mid-afternoon on Wednesday.

WHAT IS A SOUTHERLY BUSTER? READ MORE IN OUR STORY FROM DECEMBER 2024

Strong winds are likely as the cool change charges up the NSW coast, and gale warnings have been issued for parts of NSW as well as Victoria's Gippsland coast. Please check the latest on our warnings page.