It will come as little surprise to most Sydneysiders but the city is tracking its hottest January on record and a final burst of heat for the month could well have the data keepers updating their records.

Sydney's top neared 30 degrees on Tuesday, with 31 forecast for Wednesday and 35 degrees on Thursday. The average daytime temperature so far in January is 29.3 degrees, or 3.3 degrees above average.

The heat has been almost unrelenting in January in Sydney, placing various records in play. Credit:Cole Bennetts

Nighttime temperatures for January are also running at almost 3 degrees above normal - at 21.6 degrees.

In combination, the average of maximums and minimums is just a shade below the record set in 2017 of 25.59 degrees, Craig McIntosh, a meteorologist with Weatherzone, said.