Temperatures in the city reached 29.6 degrees at lunchtime, eight degrees above the late-April average and half a degree warmer than May 5, 2012.

The last time Sydney has been warmer later in the autumn season was in 1986, when the city reached 29.7 degrees on Anzac Day.

Residents made the most of the warm day by flocking to parks and beaches in numbers not seen at this time of year in decades.

North-westerly winds have been dragging very warm air from western NSW, where heat has been able to build due to a lengthy run of northerly winds under clear skies (western NSW has been reaching the low-to-mid 30s).

The warm weather will not last long with a gusty southerly change this evening cooling the city by 7 to 10 degrees.

Anzac Day will only warm up to 21 or 22 degrees across the city because the southerly winds will bring cloud and a few showers.

Looking further ahead, there is some good news for those who like the warm days. Temperatures in the mid 20s are expected on Saturday and Tuesday just ahead of cooler changes.

Elsewhere in NSW, Thursday was also the warmest day in 28 years for this late in the season in Newcastle, which hit 30 degrees.

Weatherzone