About 5000 households are still without power after a ferocious storm swept through Sydney and the Illawarra.

Tuesday night’s storm generated damaging winds and hailstones after NSW kicked off summer with a scorcher, with temperatures in the high 30s and early 40s.

Thousands of homes and businesses across Sydney, the Blue Mountains, Hawkesbury and Central Coast remained without power on Wednesday after the storm.

Crews were working to restore power to about 5000 properties, after more than 650 calls for help since Tuesday.

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Among the homes hit was a heritage residence in Ashfield, Sydney’s inner-west. A blaze ignited when lightning hit the house’s bell tower during the storm.

Five firefighting crews worked to extinguish the blaze and managed to save all of the historic house, except for the five-metre bell tower, which was engulfed in flames.

The 1888 home is known as Amesbury. No one was inside at the time of the blaze.

Streets around the house remained blocked on Wednesday morning, amid fears the fire had done structural damage to the bell tower.

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The State Emergency Service had responded to more than 400 calls 6pm on Tuesday. More than a quarter of those came from the Sydney area in a two-hour period when the storm hit.

The bulk of affected homes are in the Hawkesbury region. There are also outages in the Blue Mountains and western Sydney.

Crews from Endeavour Energy will work on Wednesday to restore power to customers as quickly as possible.

People are being warned to stay at least eight metres away from fallen power lines and report them immediately by calling 131 003.

The damaging winds and lightning caused more than 300 electrical hazards across a broad area.

Many of those who lost power were also affected by Sunday’s wind storm when the state sweltered through a weekend heatwave.

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Meanwhile, most NSW residents will enjoy significantly more pleasant weather on Wednesday, with temperatures across greater Sydney unlikely to break 30 degrees.

Meteorologists are tipping the mercury to begin rising again on the weekend.

“Temperatures [will be] starting to creep up again around Saturday, just ahead of the next cold front that will be making its way through,” Bureau of Meteorology forecaster Alex Majchrowski said on Tuesday.

-with agencies