The Westcountry remained on severe weather alert despite escaping the first "Siberian" blast of the year with snow confined to higher ground and temperatures hovering just above freezing.

Elevated areas on Dartmoor and Exmoor saw up to 8cm (3in) of snow fall overnight Sunday into Monday but much of this melted away during the day. The Met Office issued an ice warning last night as temperatures were again predicted to plunge as low as -5C (23F). Forecasters said the cold snap will continue through the week with further sleet and snowfalls expected at the weekend.

Craig Snell, a Met Office forecaster, said: "We had the first significant snowfall of the season – it looked quite snowy on the webcams on the moors – but the temperature hovered around above freezing rather than below.

"The rain band is continuing to move westwards and overnight we will face a few flurries, but the risk on Tuesday morning will be icy roads where there are untreated surfaces.

"Roads will be wet from the rain today and temperatures are expected to fall below freezing – at nights we expect -1C (30F) in Exeter, and -4C (25F) or -5C (23F) in more rural spots."

The coldest recorded temperature overnight on Monday was just 0.2C at Dunkeswell, near Exeter.

Across Devon and Cornwall through the week temperatures are likely to climb no higher than 4C (39F) in the daytime.

Dartmoor National Park Authority said the snow fell on very high ground, including Princetown, Chagford and north Bovey, and didn't cause any problems for residents or motorists. Spokesman John Weir added: "It was very slushy but didn't freeze – a lot of it has cleared off the high moor because it has rained most of the day."

Sub-zero temperatures could provide the first test of Devon's 90 newly-created snow wardens and the 20 parishes which have subsequently acquired their own motorised gritting operations.

Devon County Council, which has faced criticism for scaling-down its primary network of roads to be treated, warned of "hazardous" driving conditions "off the main precautionary salting network".

Councillor Stuart Hughes, cabinet member for highways, said: "Although we're not expecting any more rain, sleet or snow there may be water run-off from fields or standing water in some places which could lead to icy patches.

"Our teams will be working flat out to ensure that our main routes and secondary routes are treated over the next 24 hours.

"The county's snow wardens should determine their local conditions and consider if there is any water on roads which could freeze."