Sydney is having its warmest mid-winter week in nine years, averaging a maximum of 20 degrees, more typical of spring.

It reached 21 degrees in the city yesterday, five above average. This takes the seven-day average to 20.1 degrees, four degrees above the mid-winter average and more typical of September.

The last time the city had a warmer week this close to mid winter was in 2003, when it averaged a maximum of 20.3 degrees. The only other warmer mid-winter week in 150 years of records was in 1921, when maximum temperatures averaged 21 degrees.

There have been more recent warmer July weeks, in 2009 and 2005, but these were at the end of the month.

This past week in Sydney included the warmest weekend in two months, reaching 23 degrees on Saturday and 20 on Sunday.

An unseasonably warm airmass has combined with clear skies, generated by a high pressure system over the Tasman Sea.

Unseasonably warm weather will continue today, but cloud will increase in the afternoon ahead of a cold front.

This front will bring an end to the mild and sunny days today. Brisk southerly winds, cloud and showers will keep the city to about 16 degrees, close to average.

Thursday will be the start of a run of near-average maximum temperatures with help from persistent southerly winds. These southerlies will be maintained buy a low pressure system forming off the New South Wales coast. Unfortunately for most people it will make this weekend a bit breezy with a few showers about, quite a contrast to last weekend.

– Weatherzone