Commuters faced treacherous conditions during the morning with hail stones blanketing many areas after a thunderstorm tracked across Devon and Cornwall during the early hours.
The icy conditions are thought to have caused a major crash which closed the A38 near Plymouth for more than ten hours, resulting in massive jams throughout the city and beyond.
The main route between Exeter and Plymouth was dogged by accidents throughout the day with drivers losing control on icy patches or standing water.
Many schools, most on Bodmin Moor in Cornwall, also had to be closed or delayed opening as the region suffered its worst disruption of the winter so far.
The most serious accident, on the Exeter-bound carriageway of the A38 between Marsh Mills and Manadon, Plymouth, left a 42-year-old man fighting for his life in hospital.
Devon and Cornwall Police said there were five, two-car crashes within minutes of each other on the same stretch of road shortly before 6am.
It was announced last night that the driver had died. The road was finally reopened at 4.30pm just before the evening rush hour.
It was one of countless incidents reported to Devon and Cornwall Police as people struggled to cope with the icy conditions.
The A380 in Torbay was closed in both directions for almost two hours from 7.40am after a heavy hail storm hit the area and froze, causing chaos as people tried to get to work and school.
A spokesman for Devon and Cornwall Police said: "Drivers should not have been surprised by the difficult driving conditions, most of which appear to have been caused by the hail which fell on already frozen surfaces.
"Even minor collisions can cause traffic mayhem because of the obstruction and difficulty in removing damaged vehicles from the scene.
"Officers always work as quickly as they can but the key to keeping traffic moving is to prevent collisions happening in the first place.
"We would encourage drivers to think very carefully about delaying their journeys, finding alternative routes or modes of transport, in these kinds of conditions."
The Met Office said the hail storm first hit the region at around midnight with a second wave at around 6am.
It caused incidents throughout the morning on the A38. Another accident happened at around 9am at Deep Lane, forcing police to close one lane of the Plymouth-bound carriageway.
Less than two hours later, and as persistent rain fell, a car aquaplaned on the A38 at Heathfield, near Newton, left the road and ended up in a ditch.
There was another accident when a white Mini hit a crash barrier and spun into the road on the A38 between Ivybridge and Wrangaton heading towards Exeter. The incident happened at around 11.40am.
There was also an accident on the A380 at the top of Telegraph Hill heading towards Exeter. A BMW hit a crash barrier by the Texaco garage and ambulance crews were called. The driver suffered a minor back injury.
A lorry also jackknifed on the A30 near Sourton, West Devon, blocking both lanes for almost two hours.
Police said the heavy goods vehicle had lost control in "heavy snow" at around 12.30am. The driver was trapped in his cab and had to be cut free by firefighters although his injuries are thought to have been minor.
In Cornwall, the roads through Millbrook and nearby Antony, in South East Cornwall, were reportedly gridlocked at 7.40am because of ice. One lane of the A38 at Dobwalls was also closed shortly before 9am because of the slippery conditions.
Gritting teams in both counties have been working round-the-clock to keep the main road network clear amid warnings that conditions may get worse.
Devon County Councillor Stuart Hughes, Cabinet Member for Highways and Transportation, said: "The mix of rain, sleet and snow is making it difficult for our highways teams, and travelling conditions could become hazardous, particularly during the morning.
"Even though temperatures may not be as low as we've had recently, everyone should be prepared for the possibility of travel disruption and plan their journey accordingly. Please keep an eye on the forecast, be alert to the conditions and allow extra time for your journey."
As the snow, hail and ice melted it was replaced by heavy rain causing surface flooding in some areas.
Trains on the Tarka Line in North Devon were temporarily suspended, with buses replacing trains between Crediton and Barnstaple, because of rising flood water at Copplestone.
Meanwhile, 21-year-old Matthew Shipton 21, from Callington, South East Cornwall, saw his car catch fire on Dartmoor as he headed home from work at Bovey Castle. His bosses had let him finish four hours early due to the bad weather.
Later in the day, the Environment Agency issued a flood warning – the second highest – on the River Clyst, saying it had "responded to today's rainfall and snow melt". A lesser "flood alert" was also issued for the River Culm.
With more severe weather on the way, the planned overnight closure of the A30 westbound, from Daisymount junction to the junction of the A30 near junction 29 of the M5, was cancelled.
Devon County Council said the work, to replace overhead gantry signs, would restart as soon as the weather permits.
The weather also put paid to last night's Blues Brothers UK show at the Hall for Cornwall.
