Snow and ice could lead to disruption from Monday evening with up to 20cm (7.9 in) on high ground in north Wales.
The Met Office has issued a weather warning for Conwy, Denbighshire, Flintshire, Gwynedd and Wrexham between 19:00 GMT on Monday and 10:00 on Tuesday.
Ice could form on untreated surfaces on Tuesday morning as rain, sleet and snow begin to clear, the forecaster said.
It added that travel delays on roads, rail and air travel were possible, while power cuts could also occur. Some rural communities could also become cut off, the Met Office warned.
Some snow could accumulate in lower areas, which would prove “more disruptive”, although this was more likely to occur in central and eastern parts of England.
The Met Office warned drivers to plan their journeys in advance, to check for delays and road closures.
People were also being told to prepare for potential power cuts at home.
