It was the perfect combination for potentially disastrous fires - hot temperatures, low humidity and gusty winds.

A small blaze at a Balgownie reserve was quickly extinguished by multiple crews at about 3.30pm and earlier in the day a 50 square metre fire was put out at Hooka Creek Rd in Berkeley.

Read more: Illawarra residents brace for 'catastrophic' fire conditions

In the Balgownie incident, police said a teenager, aged about 15, was seen leaving the Doonan Place reserve on a bike shortly before the Balgownie Fire and Rescue crew arrived.

Detectives investigated the scene and canvassed the area.

Trucks from Mount Keira and Bulli RFS and a Corrimal Fire and Rescue NSW crew worked quickly to extinguish the blaze using live reels.

Nearby resident James Reveley smelt smoke and heard fire engines and sirens come hurtling down the road.

He said it was "frightening" and "scary" to hear those sirens so close to home.

"The response was amazing. Crews were here in no time at all," he said.

Hundreds of Illawarra RFS volunteers and Fire and Rescue workers were on standby to extinguish any blazes throughout the day and into the evening.

The message from RFS was to not become complacent because the weather conditions experienced on Tuesday were only the start of what is to come throughout the rest of spring and summer.

RFS Illawarra deputy group leader Ross Leonard said there were 30 members stationed at Helensburgh to do patrols every hour around the town and surrounding areas.

He said Helensburgh, Austinmer and Farmborough Heights crews along with police, National Parks and Wildlife Service and Fire and Rescue were targeting the main hotspots.

"We do patrols to be out there, to be seen and to have quick response time if anything happens," Mr Leonard said.

"If the winds pick up, an ignition could be from power lines, cigarette butt out the window, somebody who has been negligent with a fire pit or barbecue, or tradesman using electrical tools.

"We can also give good community education to people about their bushfire plan and it reinforces the message that we are here to help and protect them."

Helensburgh resident Kimberley Jones was working from home to look after her children while they were home from school.

Several Illawarra school were closed to the fire danger risk.

Ms Jones was vigilantly checking RFS updates.

"I am a bit concerned about the risk of fires but I passed the RFS station and they were well-equipped and prepared," she said.

"I got the texts, alerts and email. I'm just watching and waiting but we are ready to go if we need to."

Ms Jones said she had her essential items and pets packed and would go north or south depending on if and where a fire broke out.

Helensburgh RFS captain Greg Chrystal said residents should not become complacent with their bushfire plan just because there has been no major incident since 2001.

"More than half of the population in Helensburgh weren't here in 2001," he said. "Complacency has set in."

The captain reminded people to have a plan and proactively visit the RFS website, social media platforms and Fires Near Me app.

Mr Leonard said Illawarra crews were gearing up for a busy peak fire season.

"This was a lead up to it," he said. "A lot of crews from the Illawarra have gone up to the northern fires so our training has been kept up.

"Our community engagement projects have been fantastic and we will continue to push those messages.

"We don't want to send out the message that 'this is as bad as it gets' because this is just the beginning of what is predicted to be a long fire season."

A total fire ban remains in place for Wednesday.