A 35-degree day for a mainland capital city wouldn't normally be news in the first week of autumn, but when it comes to Sydney, it's a different story.

Sydney is heading for a top of 35°C this coming Monday, which would be the first time the mercury at the city's Observatory Hill weather station has reached 35°C since Australia Day (Jan 26) 2021.

If you're a regular reader of Weatherzone's news feed, you'd know that Sydney just went 331 days between 30-degree days, the second-longest such streak on record.

So it's not too remarkable that we'd be looking at a 769-day run between days of 35°C or higher if Monday reaches that mark.

Image: Our hot tip is to get there early if you want Bondi Beach looking like this. Source: Pixabay.

All the same, the hot day may come as a shock to heat-starved Sydneysiders, who have seen temperatures moderated in recent summers by La Niña's cloudy weather.

Monday's synoptic chart gives a good indication of what's happening, with hot air from the interior being pushed towards the east coast ahead of a cold front. The passage of the front will knock midweek max temps down to the low 20s in Melbourne and Adelaide, and Canberra.

Sydney will be spared the cooler temps, with maximums remaining in the high 20s next week, although days will still feel cooler after the scorcher on Monday.

Sydney's west will be even hotter, with temperatures approaching 40°C on Monday and remaining in the low 30s for much of the week.

There is likely to be extreme fire danger in the national parks flanking Sydney on Monday, so please check our wearnings page.