Rain and thunderstorms have been predicted for the drought-stricken, northern regions of NSW, and while it will be a welcome relief to farmers and firefighters, it won't be enough to break the dry spell.

Sydney is expected to get patchy showers this weekend, with rain to intensify on Saturday afternoon, especially across its northern and western suburbs.

Steph Spackman, a duty forecaster at the Bureau of Meteorology, said a low pressure system was developing over north-west parts of the state, including Narrabri, Moree and Gunnedah, which will deliver "moderate" but much-needed rain.

Weather stations near Gwydir in the North West Slopes collected about 2-5mm between 9am and 12pm on Saturday.

"We're expecting rainfall, particularly in the North West and North West Slopes and Plains, to be around the 10-15mm mark," she said.