A number of yellow weather warnings are also in place for snow and ice - with the largest area covered being the majority of England including the southeast from early this morning and until midnight tonight.
Britain was braced for further travel disruption as the "mini beast from the east" was expected to bring up to 25cm of snow to parts of the UK.
Charlotte Armitage, citizen science officer for the Woodland Trust, told the Metro: 'When we get prolonged mild periods as we have done recently, plants and wildlife are fooled into thinking the seasons are changing and start to become more active.
Many big sporting fixtures, including Ireland's Six Nations triumph over England and Manchester United's quarter final FA Cup fixture with Brighton, were played in snow storms.
By this afternoon, most of England will be hit with wintry conditions which are set to continue across the weekend and ruin any plans you had for St Patrick's Day.
Up to 10cm (4in) of snow could fall in some parts of the country this weekend as temperatures are set to tumble.
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A live webcam shows the scale of the snow and bitterly cold temperatures striking iconic tourist landmarks such as Tower Bridge.
"Windy with significant wind-chill, as temperatures struggle to exceed freezing across many areas".
Freezing temperatures brought on by the "mini Beast from the East" just days before the start of spring could have serious consequences for wildlife, experts have said.
"This decision enables us to provide more certainty to passengers around departing flights, whilst ensuring safety and service standards despite the challenging conditions".
"Our teams will be working throughout the night to keep our runways and taxiways operational and we will be closely monitoring the weather forecasts with our on-site Met Office".
Gatwick Airport tweeted on Saturday night: "Gatwick is now operating a normal service, however the weather is predicted to deteriorate and all passengers are strongly advised to check with their airline for the latest flight information before leaving for the airport".
"Keep your distance and reduce your speed, because even in conditions that seem normal, and where the snow is not settling, it can be slippery if ice patches have formed, or where fresh grit has not been worked into the carriageway".