Electric Gardens in Centennial Park and Hardcore Till I Die at the Sydney Showground in Olympic Park will each be held on Saturday, while Rolling Loud Australia festival takes over the Homebush venue on Sunday.

Three critical care doctors, a critical care paramedic and four emergency nurses will attend each event alongside festival medical teams, while thousands of bottles of free chilled water will be available to crowds.

There will also be shaded "chill out" spaces, phone charging facilities, first aid kits and free electrolyte drinks.

"NSW Health has put multiple harm reduction measures in place ahead of what is forecast to be a very hot long weekend, to do all we can to prevent deaths at these events," chief health officer Dr Kerry Chant said in a statement on Friday.

The department has launched a social media campaign - featuring doctors, paramedics and a young drug overdose survivor - as a reminder to those engaging with "party drugs" to seek help quickly if they feel unwell.

"MDMA can kill," Dr Chant said.

"If you or a friend is confused, dizzy, too hot, vomiting or has a fast heart rate, get to the medical tent fast. You won't get into trouble, health staff are there to help you."

HTID festival organisers have reiterated its "zero drug policy" via a post on the event's official Facebook page.

"There is no such thing as a safe drug so don't take the gamble. Do not bring drugs into the event for yourself or anyone else. It is not worth the risk," it reads.

Additional advice messages have been posted to revellers including that there will be "no judgment" at first aid.

Five people, aged between 19 to 23, have died after suspected drug overdoses at NSW festivals since September.

The state government is refusing to consider pill testing at future events.

Australian Associated Press