NEW YORK (REUTERS) - Unusual weather is dominating the conversation on social media for the holidays, especially among millennials, who are increasingly concerned about climate change.

Yik Yak, a location-based mobile app popular with millennials, surveyed its audience and found nearly 70 per cent are worried about climate change. More than a quarter of them say their concern has grown due to the unusual winter weather this year.

In New York City, 18 degree Centigrade-plus weather is predicted for Christmas Day, potentially breaking the record high of 17.7 degrees C in 1982. In Europe, Alpine ski slopes are facing one of the warmest Decembers on record and even glacial Moscow has been chalking up above-zero thermometer readings.

That's led to a jump in the number of people posting about climate change on Yik Yak. "Climate Change is clearly an issue! It's going to be 70 degrees (21.11 degrees C) in DC on Christmas Day... I mean if that's not proof, what is?" posted a Yik Yak user from Boulder, Colorado.

Another user from College Station, Texas, wrote: "I feel like more people should pay attention to it. It's a bigger deal than people make it out to be."

Of the 30 per cent of respondents who said they were not concerned about climate change, 18 per cent said they did not know or did not care about the issue, while just 9 percent thought it was myth.

About 6 per cent said unusual weather was just a part of the earth's natural process, according to Yik Yak.

Nearly 21,000 users participated in the poll. Yik Yak polls are often used to discuss hot topics among millennials, such as Star Wars or Netflix binge-watching.

The app turned to the serious topic of climate change after Saturday's US Democratic presidential debate prompted an outpouring of Yik Yak user frustration that there were no questions about global warming and climate change.

According to the environmental advocacy group NextGen Climate, 74 per cent of voters under 35 - approximately 80 million of whom are eligible to vote in 2016 - said they would be more likely to vote for a presidential candidate with a plan to tackle climate change.

About 63 percent of young voters said they would be more likely to vote for Democratic presidential candidate Hillary Clinton if she supports clean energy goals, NextGen Climate said, based on results of a survey done in September.