Winter may be just 10 days away, but beachgoers can delay packing up their swimmers for at least another week while Sydney's unusually warm May weather heats waters off the NSW coast.

Sea temperatures on the east coast are resting at a comfortable 23 degrees, and daily maximums of up to 26 degrees are forecast throughout the week as an above-average autumn winds to a close.

Bathers enjoy warm late autumn weather at Red Leaf Beach in Double Bay, Sydney. Credit:James Alcock

Weatherzone meteorologist Brett Dutschke said sea temperatures closer to Sydney's coast were approximately 21 degrees and about a degree warmer than last year, although that "might vary slightly from beach to beach".

He said seas off the east coast had been "taking longer to cool than usual" due to a combination of warmer than average weather and a lack of low-pressure systems bringing colder water to the surface.