THE record wasn't broken but it was still a scorching day.

Ambulances were kept busy treating those overcome by heat as firefighters kept a tense standby - fearing any of 59 fires burning across NSW could erupt.

The city had been tipped to hit 39C - which would have surpassed the October record of 38.2C in 2004 - but peaked at 37.3C at 3.03pm. That was still the hottest Sydney day in nine months - since January 18's high of 45.8C.

It was also the city's third hottest October day since records began 154 years ago.

While it will be cooler today and tomorrow, the intense heat is expected to return on Sunday - when there will again be total fire bans.

By 11.30pm last night, Sydney Airport's weather station was reporting winds of up to 70km/h - gusting to more than 80 km/h. At nearby Port Botany, wind gusts were approaching 100km/h.

An SES spokeswoman said volunteers would be on-call throughout the night but had not yet received any distress calls.

The official Twitter account of Centrepoint's Sydney Tower Eye read last night: "Wow. The southerly change just hit Sydney like a bulldozer. Temperatures are plummeting and winds are howling...."

GALLERY - SYDNEY SIZZLES

media_camera Sizzling Sydney

media_camera Sara Jean and Pete Zee at Bondi Beach.

In Sydney's far west people took to pools, lagoons and rivers to cool down.

Tina Wall took her and her neighbour's children from Mt Druitt to Windsor to cool down in the Hawkesbury River, where Jarrod and Justin took the opportunity to practise their football skills in the water with neighbourhood children Mariah and Jade Wilson and Chantell Molloy.

"As soon as we heard it would be 40C we decided we would come straight to the river," Ms Wall said.

"But, today hasn't been so bad. It's more the hot wind that I'm having trouble with."

Finding a quiet, private spot to escape the sizzling heat at Bondi beach yesterday proved futile as more than 15,000 sun lovers braved the unseasonably high temperatures for a refreshing swim and sunbake. At 7pm it was still sweltering at 33C.

Yesterday's heat kept ambulance officers busy, with calls to treat 20 people for "heat exposure'' across NSW.

media_camera Guido Ferri at Cinque e Mezzo sweating it out in his Pizzeria. Picture:

Many of the calls for help from ambulance officers came from beachgoers, with calls to Maroubra where a 25-year-old man passed out on the beach, at also to Bondi, Avalon and Coogee beaches.

In contrast, tiny surf meant there was "not one major rescue" on Sydney beaches up to 5pm, a Surf Life Saving NSW spokeswoman said.

media_camera William Sherd 5 and his brother Zac 3 cool off at Lake Cathie on the NSW mid north coast.

Almost all tracks and trails in Sydney's national parks were closed yesterday to prevent deliberate or accidental fires, as were some Harbourside vantage points to watch the Tall Ships depart the Emerald City.

A man and a woman were arrested near where a bushfire was burning in Cessnock yesterday afternoon and were being interviewed by police.

Power usage soared in the afternoon, with NSW gobbling up about 10,200 megawatts after 4.30pm as home airconditioners were switched on.

media_camera Figure Skaters Alex Jackson (L) and Sarah Cullen chill out at Erina Ice Arena during the Heat wave on the Central Coast.

The hottest temperature in NSW yesterday was recorded at Wilcannia in the northwest, where it reached 42C.

Bureau of Meteorology forecaster Chris Webb said the temperature didn't reach its predicted record peak in Sydney because there was some cloud around midday.

For some Sydneysiders yesterday's heat brought treats and special care.

Taronga Zoo's koalas enjoyed a sprinkler wafting cool water over their trees, while the 17-strong chimpanzee troop were handed frozen fruit juice and three small-clawed otters sucked on "fish-cicles" made of frozen pilchards.

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SYDNEY SWELTERS: Send your hot weather pictures to photo@dailytelegraph.com.au

media_camera Explosive situation as temperature hits 34C

media_camera Senior Constable Anthony McLachlan rubs water on his dog "Belle" while Constable Jared Rodger gives his dog "Bear" a drink after training in Centennial Park.

media_camera Mona Vale Beach. Picture:

media_camera Brayden Jacobson, 7, cools down at Newcastle Ocean Baths.

media_camera Gale force winds on Newcastle beach blew Brayden Jacobson's body board away.

#FRNSW responding with #NSWRFS to a house #fire, Bringelly. 2-storey house well alight, fire fighting ops. underway. — Fire & Rescue NSW (@FireRescueNSW) October 10, 2013

Range Rd Fire: (Singleton) #NSWRFS on scene at a fire in army range. Crews unable to directly access area due to unexploded ordinance. — NSW RFS (@NSWRFS) October 10, 2013

#asnsw paramedics have so far treated 10 cases of heat exhaustion, including 8 in the Sydney Metro area. Also 36 cases of fainting/dizziness — Ambulance NSW (@ASNSW) October 10, 2013

An Antanov has landed in #Sydney with two Aircranes on deck. First will start service next week. #NSWRFS #nswfires pic.twitter.com/A348FHMQHe — NSW RFS (@NSWRFS) October 9, 2013

media_camera Sydney braces for a scorcher

media_camera The tractor was out to prepare the sand for an influx of visitors seeking to beat the heat today at Bondi Beach. Picture: Bill Hearne