Sydney's long, hot summer shows no sign of wavering in its final days, bringing with it some unwelcome guests.

Beachgoers who head to the coast to make the most of the last weekend of summer can expect sunny skies and warm temperatures, as mild weather heats up in coming days.

However they have also been warned to look out for bluebottles, with lifeguards at North Bondi dodging big waves, as well as armadas of the creatures strewn across the sand this week.

Weatherzone meteorologist Kim Westcott said north-easterly winds sweeping through the city would keep a lid on hotter temperatures in the city, but the west was set to swelter.

"For Sydneysiders, the week has been quite cool. It's been a nice reprieve and not too humid.

"It will be a nice, brief spike [of heat]," she said.

A forecast maximum temperature of 27 degrees in the city and 33 degrees in Penrith on Friday would warm to predicted tops of 31 degrees in Sydney's centre and 38 degrees in the western suburbs on Saturday.

"It will be mostly sunny and a little dusty.

"It will be a little bit windy but that sea breeze won't really do much, the heat will still be quite intense."

Temperatures will hover around 30 degrees across the city as showers, bringing between six and 20 millimetres of rain to parts of the Sydney Basin, fall throughout Sunday.

The mercury should take a brief dive on Monday, with a forecast maximum of 24 degrees in the city and 29 degrees in the western suburbs.

The weather will heat up again mid-week as the mercury reaches 32 degrees in the city, and 39 degrees in Penrith.

"Temperatures rise quite swiftly on Wednesday and Thursday, when the heat will be quite intense."

Swimmers can also look forward to warmer waters off the coast, with offshore temperatures hovering around 23 and 24 degrees as the weekend approaches.

Winds that swept across the coast also swept in bluebottles, which could be found dotted along beaches from Cronulla to the city in the past week.

Surf Life Saving NSW spokeswoman Donna Wishart said prevailing north-easterly breezes in Sydney throughout summer scattered "big lots" of the jellyfish along sandy stretches.

"Basically they drift in with the wind and the currents, it's just luck where they land."

Ms Wishart said swimmers who got stung by the sea creature should wash the tentacle from their skin with seawater or pick it off with their fingers to remove the toxic prong.

"Put it under the hottest water you can stand for about five minutes or more to get most of the pain and the toxins out of it."

Weatherzone is owned by Fairfax Media, publisher of the Sydney Morning Herald.