The burst of heat that seared Sydney over the weekend will give way to days of heavy showers, according to the Bureau of Meteorology.
Sydney on Monday fell shy of hitting three consecutive March days of 30 degrees – which would have been the first such trio in the month since 1902 – with a top of 28.4 degrees.
A wind shift from the north-west that had brought warm air from central Australia to an easterly flow put a cap of temperatures.
Tuesday's forecast top of 27 degrees will make way for three days of about 23-24 degrees, with rainfall totals mounting as a low-pressure trough moves in.
Tomorrow could see Sydney collect 15-25 millimetres and Thursday 25-45 millimetres, the bureau said.
"At this stage, it looks like [the trough] will have the biggest impact on the central coast and possibly even further north," said Rose Barr, a duty forecaster at the bureau.
"It is dependent on where this coastal feature develops."
The system is not likely to take on the form of an east coast low, Ms Barr said, noting the absence of upper-level conditions conducive to the more extreme rains and wind.
The heavier falls are likely to come from thunderstorms developing within the system, Ms Barr said.
Temperatures should begin to climb again by the weekend, with tops in Sydney of 26 and 30 degrees currently forecast for Saturday and Sunday, respectively.
It's unlikely Sydney will see a repeat of last weekend's heat, which included its hottest day this late in the season – 39.4 degrees on Sunday – since 1940.