Cool but short-lived change for Sydney

Sydneysiders will be given a cool reprieve from the sweltering temperatures on the weekend but it will be short-lived.

The temperature will drop to the mid-20s in Sydney and high-20s to low-30s on the western outskirts on Saturday.

Western parts of NSW, including Broken Hill and Cobar, will scorch in temperatures of 40C plus.

Those conditions will sweep across to the coast and drive up temperatures in the eastern areas on Sunday.

Sydney is expected to reach 35C on Sunday while Penrith could tip 40C.

Bureau of Meteorology forecaster Mohammed Nabi said there will be a severe fire danger in the central, northern metropolitan and lower Hunter regions on Sunday.

"There is a very high fire danger in parts of the state on Saturday but it's on Sunday that things start to get interesting," he said.

Penrith reached 41C on Friday while Walgett in the northwest tipped 42C.