Michael Dukes, director of forecasting at MeteoGroup said the cold snap was due to remain for "some time yet".
There has been a band of sleet and snow moving through parts of the east Midlands, east England and south east England late in the night, towards morning.
It has produced only one or two centimetres in places, it is not very much. Most of the snow has been on higher ground but there has been a little bit of snow on lower ground as well.
More top news
Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.
The violence began after a counter-protester allegedly doused a female rally organiser with pepper spray.
As temperatures climb through the day, the warmest spots are likely to be across western parts of Northern Ireland and western Scotland.