More than 7000 homes are still without power after wild weather lashed Sydney and surrounding regions on Friday, as cool relief from Sydney's heat approaches.

Severe thunderstorms hit Sydney on Friday evening, producing heavy rainfall, damaging winds, and large hailstones, with some suburbs receiving as much as 60 millimetres of rain between 6 and 9pm.

Lightning from storms as they passed over Sydney. Credit:Nick Moir

At least 15,200 homes and businesses on the Ausgrid network in Sydney, the Central Coast and the Hunter regions, as well as 28,700 Endeavour Energy customers across the Blue Mountains, Southern Highlands and the South Coast, lost power.

As of 8.30am Saturday, about 2000 Ausgrid customers in Galston, Hornsby Heights and Berowra were still without power.