A spell of unseasonably warm weather is expected to continue across the Hunter this week with temperatures tipped to reach the low 20s on most days.
The mercury reached 24 degrees at Nobbys on Sunday afternoon, well above the July average of 16.8 degrees.
The hottest July day recorded at the weather station was 26.3 degrees on July 24, 1990.
Cessnock and Tocal recorded 24.4 degrees, while Williamtown recorded 24.8.
The Hunter's hotter than average conditions are expected to continue throughout spring and into summer as an ElNino weather pattern takes hold.
Internationally, July is set to be the hottest month ever recorded with the United Nations chief declaring an "era of global boiling" has arrived.
The month has already set records for the hottest three-week period, the three hottest days and the highest ever ocean temperatures.
UN Secretary-General Antonio Guterres has used the news to issue a rallying cry to global leaders.
"Humanity has unleashed destruction. This must not inspire despair, but action," he said. "We can still stop the worst but to do so we must turn the year of burning heat into the year of burning ambition."
Mr Guterres said the consequences were clear and "tragic".
"Children swept away by monsoon rains, families running from the flames, workers collapsing in scorching heat," he said. "For the entire planet it is a disaster."
People across the US, Asia and Europe have sweltered through extreme heat in the past month.
A remote Chinese town set a national record with a 52.2 degree day and in the US tourists gathered in California's Death Valley as the mercury soared to 53 degrees.
Wildfires have raged across southern European countries including Greece and Italy, while in South Korea torrential rain and flash flooding left 40 people dead.
Mr Guterres called on nations, including G20 countries which are responsible for 80 per cent of global emissions, to act with urgency.
"Climate change is here. It is terrifying and it is just the beginning," he said. "Leaders must lead. No more hesitancy, no more excuses. No more waiting for others to move first, there is simply no more time for that.
"It is still possible to limit global temperature rise to 1.5 degrees and avoid the very worst of climate change but only with dramatic, immediate climate action."
He said new ambitious national emission reduction targets were needed and commitment from developed countries to reach net zero as close as possible to 2040.
An equitable transition from fossil fuels to renewables was vital, Mr Guterres said.
He also urged companies, cities, regions and financial institutions to step up, with "no more greenwashing".
And with extreme weather becoming the "new normal" the world must be prepared.
"All countries must respond and protect their people from searing heat, fatal floods, storms, droughts and raging fires," he said.
Mr Gutteres said unprecedented coordination was required to save millions of lives from climate change.
This included having every person on earth covered by an early warning system by 2027.
