GENEVA

As millions in the Northern Hemisphere grapple with record-breaking temperatures, the UN issued a warning Tuesday that increasingly severe heat waves could be on the way.

"We are seeing continuing growth in the frequency, duration and intensity of heat waves," said John Nairn, a senior extreme heat advisor of the World Meteorological Organization.

"These events will continue to grow in intensity, and the world needs to prepare for more intense heat waves," Nairn told a UN briefing in Geneva.

On heat-related deaths, he said that a recent study calculated that in Europe, there were 60,000 additional fatalities last summer due to extreme heat.

Noting that the figure was limited to Europe, the advisor said heat waves were becoming more widespread around the world.

He emphasized that Europe has "some of the strongest early warning systems and heat health action plans in the world."

"So, you can imagine what the numbers are likely to be globally," he added.

Nairn said the growth in simultaneous heat waves around the Northern Hemisphere had increased six-fold since the 1980s, with no sign of decreasing.

Currently, July and August are the most critical months for extreme heat waves, he added.

The WMO said Monday that new record-high temperatures could be recorded as intense heat waves grip the southern US, Mediterranean, North Africa, Middle East, and some countries in Asia.