Winter put on hold as Sydney basks in warm May sunshine

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

May's warm weather has put Sydney on track for its fifth month of above-average maximum temperatures this year.

It's so warm that Sutherland Council lifeguards have put up their surf swimming flags on North Cronulla Beach to help beachgoers swim in a safe place.

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 above-average autumn winds bring the season to a close.

Weatherzone meteorologist Brett Dutschke said sea temperatures closer to Sydney's coast were about 21 degrees, 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.

"The east coast has been warmer than normal for several months, but it's warmed up in the past week or so off the NSW coast because of a lot of sunshine," Mr Dutschke said.

"We haven't had a string of overcast days, so that sunshine has kept the surface of the water nice and warm."

Sydney has only had one day this month below the long-term May average maximum of 19.5 degrees, while the rest of May has hovered about 3 degrees above. Maximum temperatures as high as 26 degrees - up to 6 degrees above average - are forecast for the week ahead.

Mr Dutschke said this meant prevailing water temperatures off the NSW coast would remain a couple of degrees warmer for at least another week, and could potentially inch slightly higher.

"It might even last well into June," he said. "There are signs of a cold front coming but it will probably stay warmer than average for much of winter, depending on how many low-pressure systems we get off the coast. That's largely based on how long it has been warmer than average over past months."

May's warm weather has put Sydney on track for its fifth month of above-average maximum temperatures this year.