Snow today, then rain will speed the thaw

A flurry of snow is expected across much of Britain today and tomorrow before giving way to a thaw, albeit temporary. Up to 5cm of snow is forecast to fall across eastern and northern parts of the country, with up to 20cm in parts of Scotland and 15cm on the Pennines and Yorkshire Moors.

The Met Office says the fresh snowfalls are the last "in the foreseeable future", but a fresh bout of freezing weather will set in by the end of the week in time to cool down plans to celebrate the start of the new year.

Rain forecast for the South-west should mean snow and ice on the ground will melt quickly, causing some localised flooding. But major and widespread flooding is unlikely, since about 10 inches of snow are required before melting to make one inch of water.

Officials at the Environment Agency anticipate a handful of low-level flooding alerts but are not expecting serious problems even where rain adds to meltwaters.

A spokesman said: "Rain is expected on Tuesday, increasing the rate of snow thaw in South-west England and parts of Wales, leading to a low risk of flooding in these areas."

There will be a respite in some parts of the country, especially in the west, by the middle of the week. Devon and Cornwall will be the warmest, reaching temperatures of 11C tomorrow and Wednesday, while other western areas, including western Scotland, could reach 7C.

Temperatures for the vast majority of the country should get above zero during daylight by the middle of the week but there will be widespread frosts at night, except in the South-west and, possibly, the South-east.

December 2010 is almost certain to go down as the coldest December since records began a century ago. The previous coldest was 1981.

By comparison with temperatures experienced in recent days the forthcoming freeze will be mild. Where night-time temperatures had slumped to -10C or -15C, at the weekend they will be more like -2C to -5C.

Easing weather conditions should be good news for the rail network, which says it should be able to run 90 per cent of its normal services from Wednesday – although commuters will no doubt believe it when they see it.

A Sunday train timetable will be run today and tomorrow. Then, rather than ice and snow, it is major engineering works this week which are expected to cause the worst delays.

Barry Gromett, of the Met Office, warned that despite warmer conditions the roads and pavements are likely to remain treacherous. "Over the next couple of nights there will be widespread ice," he said. Snowfalls today and tomorrow were "probably the last of the significant snow for the foreseeable future".