Sydney's run of well-above average temperatures is about to come to a chilly halt that will please few save those headed for the snowfields.

Every day this month has been warmer than the June average, with both day- and night-time temperatures about 3 degrees above normal.

The powerful cold front that is raising flood risks to parts of South Australia and northern Tasmania will arrive in Sydney by Friday, bringing dry westerly winds of 30-50km/h to boost the wind-chill factor.

Sydney can expect a top on Friday of 17 degrees, in line with the June average, according to updated forecasts from the Bureau of Meteorology.