Snow showers, initially affecting Northern Ireland and southwest Scotland, will progressively extend southeast to affect the rest of Britain by Thursday afternoon.
There is the potential for disruption to transport networks with longer journey times. Icy stretches on untreated roads and pavements are also possible.
Around 2 cm of snow is possible even to low levels in places. 5-10 cm is possible on high ground above about 200 m.
RAC spokesman Rod Dennis said:
“The see-saw weather we’ve seen in the last few weeks continues with a switch this week to much colder, and much more unsettled conditions for all of us.
“Even a small amount of snowfall has the potential to cause major disruption for motorists. The fact that drivers in some parts of the country will be faced with strong winds, snow showers and icy stretches increases the chances of problems on the road enormously.
“Commuters and those drivers planning longer journeys this week must heed the weather warnings and be prepared for tricky driving conditions and significantly extended journey times.
“With the possibility of problems affecting public transport networks, this will likely force more people into their cars so motorists should also not rule out more traffic on major routes.
“A lot of accidents happen when people are in rush – with conditions deteriorating this week, we strongly advise motorists to plan their trips carefully and consider rearranging any non-essential journeys in the parts of the country most likely to be affected by the bad weather.
“Drivers should take the time to check over their car now to make sure it’s in the best condition possible for the arrival of snow and ice. We recommend tyres are checked for tread and pressure, wipers for any wear, and screenwash that protects to well below freezing is topped up.
“When out on snowy roads, always have dipped headlights on and proceed carefully and cautiously – drive with a very light right foot, and keep your revs down by changing to as high a gear as possible. Try to avoid braking and turning at the same time – when approaching a bend in the road, reduce your speed first and then begin to turn. Above all, avoid the temptation to brake sharply as that will make you lose control.”