The El Nino weather pattern - initiated by a band of warm sea water developing in the Pacific Ocean - is widely believed to be behind the weather that has seen unseasonably warm temperatures experienced in parts of Europe.
But the WMO is warning that global temperatures could rise by six degrees celsius or even more, unless more action is taken to address climate change.
A global climate change summit kicks off in Paris on Monday, with WMO Director General Michel Jarraud keen to stress that there is still time to agree steps to help reduce the impact of global warming on the planet’s weather.
Mr Jarraud said: “You have scenarios assuming very strong decisions, very quick and sharp reduction of greenhouse gases, and you have other scenarios with business as usual, where you end up with predictions of additional warming of five, six degrees, maybe even more.
“That will very much depend on the decisions.”
According to the WMO, eight of the world’s ten warmest years have occurred since 2005 - a statistic Jarraud says is ‘bad news for the planet’.