Emergency crews tackled two separate crashes on the A38 just outside Ivybridge involving a total of nine vehicles caused by the freezing rain and hail.
Police closed the A38 westbound carriageway at Lee Mill on Sunday night but said that nobody was trapped or seriously hurt.
Drivers were urged to avoid the road and take extra care in the treacherous conditions.
Six cars and one motorcycle were involved in a crash near the Lee Mill junction at about 6.40pm.
Three fire crews assisted paramedics with first aid and made the vehicles safe using small tools.
Firefighters from Crownhill, Plympton and Ivybridge tackled a second accident which happened at about the same time close to the nearby Smithaleigh junction.
Two vehicles were involved but everyone managed to get free of the cars.
One women and two children were suffering from shock.
Ambulance crews tended to all three casualties at the roadside.
Highways Agency staff helped the emergency services clear the vehicles and debris from the carriageway.
Devon and Somerset Fire and Rescue Service, which attended the crashes, was blaming freezing rain and hail for the collisions.
Devon and Cornwall Police shut the westbound carriageway so the crews could deal with the accidents.
They were finally reopened at around 10pm, after traffic had been diverted through Ivybridge.
A spokesman said during the incident: “Plymouth police urged drivers to avoid the area, with diversions in place at Avonwick.
A spokesman said: “We are acutely aware with rail out the A38 is a critical route.
"With this in mind we will ensure this incident is fully resourced to clear it as soon as possible.”
Chief Inspector Ian Drummond-Smith said there had been a “hail storm” causing multiple crashes. He urged motorists to drive very carefully.