Heavy rain had made roads around the venue impassable, the group said.
The cancellation came after Storm Dennis brought flooding and dangerous weather conditions to the UK, prompting the Environment Agency (EA) to issue more than 200 flood warnings.
Sophia Coningham, a 15-year-old climate activist from London, said there was a “bleak irony” in the conference being shut down by extreme weather.
“This kind of last-minute cancellation is particularly difficult for young people without the financial resources to travel across the country whenever we choose,” Sophia said.
“We are now living in an age of climate storms - where the most extreme weather of the last century is becoming the norm in this one,” she added.
“This is an emergency that’s now being felt across the world - from Staffordshire to Sri Lanka.”
Earlier today, Dr Michael Byrne, a lecturer in climate science at the University of St Andrews and research fellow at the University of Oxford, warned that more water in the atmosphere is “an entirely inevitable consequence of climate change."
“When you warm the planet, the atmosphere holds more water. In many parts of the world, including the UK, rising temperatures go hand in hand with more rain,” he said in the wake of two major storms (Dennis and Ciara) in recent weeks.
He said it was unclear whether climate change would strengthen or weaken high winds from major storms, but added that there would be more rain associated with such incidents.
“These storms are nothing new, going back 100 years, but, because we are now more than 1C warmer as a whole versus pre-industrial times, every degree means 7 per cent more water in the atmosphere and more rain in these heavy rain events,” Dr Byrne said.
“When they come, they bring more rain, 100 per cent for certain, because of climate change.”
John Curtin, the head of floods and coastal management at the EA, said on Monday that more than 400 properties had been flooded following the storm and added that the number of homes hit was “likely to rise”.
The EA has also warned torrential rain from the storm has swelled rivers to “exceptional” levels in parts of the UK, with more rain forecast to fall later this week.
South Wales, Herefordshire, Worcestershire and Shropshire are among the worst affected areas from the extreme weather over the weekend.
One woman, who was swept away by floodwater in Worcestershire on Sunday, has been presumed dead by police as search efforts resumed on Monday.
Additional reporting by PA