The 72-year-old man and 13-year-old boy were reported missing in the Warrumbungle National Park on Sunday afternoon, when they failed to return home in time.

Search and rescue teams were activated after a triple zero call just before 4pm.

There were fears for fading light but police, paramedics and SES crews were deployed to the search area, while the Westpac Rescue Helicopter was also tasked for an air search.

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In the midst of temperatures nudging 40 degrees, ground crews managed to find the missing bushwalkers near a campground in the middle of the park, west of Coonabarabran.

A spokesperson for Ambulance NSW said paramedics treated both bushwalkers for minor injuries and assessed them for dehydration.

The teenage boy was then taken to Coonabarabran hospital for further treatment. He was said to be in a stable condition.

Rescuers said luckily it ended well, but hikers, walkers and sightseers are being urged to get prepared before they set out in the soaring heat.

Emergency services said heat exhaustion and dehydration could take hold quickly, especially in the current heatwave baking Western NSW.

Those considering going on a hike should check the weather forecast regularly, and know when to turn around or take a break.

NSW Police urged bushwalkers to follow several safety tips including:

NSW National Parks and Wildlife also recommend researching the trail ahead of time, and to bring at least 2 litres of water per person, a first aid kit and food.

Fire and Rescue NSW encouraged everyone to download the Emergency Plus app in case of a need for rescuing.

- with Jessica McLaughlin