Temperature will be close to normal for mid-March with highs of 12C.
Some areas may remain cloudy and damp through the afternoon but it will be mild with highs reaching 14 Celsius.
Heavy rain will hit the whole of the country on Sunday.
Major incidents have been declared in south Wales, Herefordshire, Worcestershire and Shropshire after Storm Dennis battered the UK.
The fourth named storm of the 2019-20 season, Dennis, is set to bring a second consecutive weekend of wet and windy weather.
The top temperature across the UK on New Year's Eve is expected to be 11C.
The south will see brighter skies than the north on Christmas Eve.
The showers will be heavy at times, with the risk of thunder.
Storm Atiyah approaches parts of Wales and south-west England later on Sunday.
Sunday will see top temperatures of 8 Celsius (46 F).