The weather bureau has issued a severe weather warning for damaging winds affecting almost the entire state amid a total fire ban across Sydney and much of NSW's north on Friday.

The temperature in Sydney is forecast to hit a maximum of 29 degrees ahead of a strong cold front sweeping from the state's west and generating vigorous winds.

Wind-blown sand streams down Prince Charles Parade in Kurnell last month. Credit:Nick Moir

In a severe weather warning, the Bureau of Meteorology said damaging winds averaging 60 to 70km/h with peak gusts in excess of 90km/h were possible for south-western NSW and eastern districts on Friday afternoon and evening; possibly also stretching over the northern ranges into the evening.

The damaging winds will ease in some parts overnight, but are set to remain over the Central Ranges and south-eastern districts on Saturday, with gusty winds remaining for the Sydney coastline on Saturday afternoon.