The Sydney region will enter spring primed for large bushfires after its third dry winter in a row, with maps showing moisture levels are below those in the run-up to the blazing 2013 season.

Moisture levels of trees and other live vegetation for the fortnight up to August 12 show much of the region around Sydney to be dry, particularly to the north-west and in the Blue Mountains.

The dry conditions mean it is likely all forested areas in the state will have the start of their dangerous bushfire period brought forward to September 1, the NSW Rural Fire Service said.

A bushfire near Springwood in the Blue Mountains in October 2013. Dry conditions this winter have fire experts wary of the coming season. Credit:Dallas Kilponen

"It's dry across the Sydney basin," said Rachael Nolan, a fire ecology lecturer at Western Sydney University who compiled the data from satellite imagery. "Our research shows when the live stuff dries out, you're more likely to get the more severe fires."