Britain has marked its hottest New Year's Eve on record, the UK Met Office has confirmed.
The previous record of 14.8C, held by Colwyn Bay in North Wales in 2011, was toppled at 11am in Ryehill, East Yorkshire, when the mercury hit 14.9C.
The following hour a high of 15.3C was recorded in Coningsby, Lincolnshire.
Meanwhile, Ireland also saw double digit temperatures for many parts of the country, with temperatures passing 14C.
Today's maximum temperature of 14.6C at the Phoenix Park in Dublin is short of the record for New Year's Eve in Ireland.
That still stands at 16.5C, which was recorded at Waterford Airport on 31 December, 1987.
Met Éireann said that the nighttime temperature record of 11.4C may be beaten, as it forecast a mild night across the country.
It said: "Temperatures tonight won't drop much from this afternoon, staying very mild overnight with lowest temperatures of 9 to 12°C.
"This may challenge the record for the warmest New Year's Eve night in Ireland."
The warmer than usual temperatures are due to what Met Éireann said was a "stream of mild air originating from further south in the Atlantic ... pulled up over Ireland and over parts of Europe by a strong southwesterly airflow".
It comes on the day Met Éireann issued its annual weather and climate review, which showed 2021 was "provisionally the warmest autumn on record and another warm year for Ireland as a whole".
Most places will have a dry afternoon with some brightness & just a little mist or drizzle here or there.— Met Éireann (@MetEireann) December 31, 2021
Becoming windier this evening with fresh to strong southerly winds developing, reaching near gale force near southern & western coasts. Very mild, with temps of 11 to 14°C. pic.twitter.com/e4pg35mIiE
Temperatures will continue to climb across Britain later in the day before falling slightly at night as the UK rings in 2022, according to forecasters.
Areas of southern and eastern England, including the West Country, London and Lincolnshire, are set to experience the warmest weather.
"Our station at Ryehill, a small village in East Yorkshire, has recorded 14.9C today, which tops the previous record of 14.8C. It has provisionally broken the New Year's Eve record," Met Office spokesperson Stephen Dixon said.
Provisionally, Coningsby in Lincolnshire has recorded 15.3 °C so far today, meaning today is the warmest New Year's Eve on record for the UK pic.twitter.com/bIjgE2vtHP— Met Office (@metoffice) December 31, 2021
"We would expect that to climb further and reach temperatures we saw yesterday of around 15.5C."
Revellers in some parts of the UK will have to brace for rain in the evening, with light drizzle expected across pockets of eastern and southern England and North Wales.
But the overall picture is "exceptionally mild", with unseasonably warm temperatures of 14.5C in Hawarden, North Wales, and 14.2C in Yeovil, Somerset, reported this morning, forecasters said.