Sydneysiders struggling back to work and school this week are likely to get little early relief - particularly overnight - from the city's record-breaking heat.

On Monday, the temperature climbed back into the 30s for the city, reaching 34.3 degrees before 1 pm. Some inland suburbs have topped 43 degrees, with Richmond touching 43.5 degrees and Camden 43.8 degrees, the Bureau of Meteorology said.

The mercury in Sydney is likely to rise to 37 degrees on Tuesday in the city, before a cool change sweeps away some of the warmth by the middle of the day, Rob Sharpe, a meteorologist with Weatherzone, said.

In between, the city can expect another sweltering night, with the minimum temperature likely to dip only to 26-27 degrees across most of the Sydney Basin.