Bushfire risk soars amid scorcher for NSW

Firefighters are bracing for scorching conditions across NSW as residents are warned to watch out for snakes and swim between the flags.

The mercury will soar to the mid-30s in Sydney on Saturday and climb above 40 degrees in some parts of the state.

"It's going to be a hot weekend and records will be broken," a Bureau of Meteorology spokesman told AAP on Friday.

Temperatures will be roughly 12 degrees above average in most parts of NSW.

Fire danger ratings could reach extreme levels as a result of abnormally hot conditions, dry vegetation and lack of rainfall.

A total fire ban has been declared for much of NSW.

Rural Fire Service Inspector Ben Shepherd urged residents in greater Sydney, the Hunter and the far west to be diligent.

Families heading away as school holidays start should stay safe and discuss their fire plans, he said.

The weekend also marks the beginning of the beach season and the return of lifesaver patrols.

"Swim at patrolled beaches and please swim between the flags," Surf Life Saving NSW chief executive Steven Pearce urged beachgoers.

"And if you're unsure, find a patrol and ask."

Soaring temperatures will lead to an spike in snake activity, with residents in both rural and suburban areas told to look out for slithery behaviour.

The Australian Reptile Park says extreme caution should be taken as warmer spring days have already led to an increase in snake activity.

"Snakes don't go out to harm humans, but if you get in their path or startle them, they will bite and it can be fatal," the park's head of reptiles Daniel Rumsey said.

Temperatures will ease after the weekend before heating up again mid-week.