Further travel disruption is expected across the UK as forecasters predict that temperatures will plummet even lower coupled with the possibility of more snow.
Overnight temperatures fell as low as -20C in Scotland, and -7C in Birmingham.
Gatwick Airport has reopened after two days of closure, but passengers are warned of delays and cancellations.
A spokesman said: “The airport has safely reopened this morning after round-the-clock working to clear snow and ice from the runway and taxiways.”
“Weather forecasters are predicting freezing fog during most of today, so passengers should expect further disruption, with flights limited and delays and cancellations inevitable.
“Passengers should also be advised that it is likely to take a few days before flight schedules return to normal.”
Southern and Southeastern rail have reduced services, trains in East Yorkshire have been cancelled, and there are few services north of Glasgow.
Overnight passengers on a Glasgow-bound sleeper train were stranded without heating for three hours when the brakes froze.
Police in Kent, Hampshire, Cornwall and Scotland warned motorists not to drive unless it was absolutely essential, due to ice on the roads.
Rail firms across the south cancelled services leaving commuters at home for a second day.
Snow showers have eased but the Met Office is now warning of widespread icy roads in south-west England.
Areas including Northern Ireland, western Scotland and north-west England are set to be hit by further snowstorms over the weekend.
Five of BAA’s six airports were open this morning (Heathrow, Stansted, Glasgow, Aberdeen and Edinburgh), but Southampton was closed for the morning but opened in the afternoon with limited service due to icy conditions.