The Beast from the East 2 is set to bringing freezing cold temperatures to Wales.
Temperatures are expected to plummet below 0°C for most of the UK. On Sunday night it was 2°C at Cardiff Airport, but with a windchill making it feel more like -4°C.
On Monday, Welsh forecaster Derek Brockway said it was -1°C in Tredegar with a windchill of -8°C.
Wales is one of the few places in the UK that has not got weather warnings for snow and ice this week, but it is still going to feel bitterly cold in the easterly winds from Russia.
Temperatures could fall to as low as -13C in some areas of the UK, with the country feeling the full effects of Storm Darcy.
The Met Office said the bitterly cold weather will be caused by strong easterly winds that have battered the country from Ukraine and the Black Sea.
The forecast for Monday is: "Bitterly cold for all. Feeling colder with wind chill in the brisk easterly wind.
"On Tuesday , cold air continues to flood over the UK, with snow showers and brisk east winds.
"On Wednesday high pressure builds in the north. Staying cold with snow showers easing through the day."
By Thursday , warm air will try to push in from the west, bringing the chance of some snow showers in the west.
On Friday , the battle between cold and milder air will continue, but the Met Office says it is too early to say how this will play out.
Forecasters are now warning of the potential for "widespread travel disruption" as well as a power cuts and service outages.
A slew of weather warnings remain in place today until Wednesday for snow and ice across many eastern parts of the country, and spanning the entire length of Britain.
Storm Darcy is the low pressure system that is bringing heavy snow and strong winds to East Anglia and south-east England, the Met Office said.
Essex, Norfolk, Suffolk, Kent and Medway are all regions which are set to be hit by an "area of widespread, persistent and occasionally heavy snow" through to Monday, according to the amber warning.
Weather in your area by postcode:
Here is the five-day Met Office forecast for the UK:
Today:
A frosty start, with cloud slightly clearing across the country allowing for sunny spells. Snow showers across northern and central areas, drier in the south and westernmost areas. Southern coastal gales, and strong winds throughout, feeling bitterly cold. Maximum temperature 3 °C.
Tonight:
This evening and tonight, snow showers will continue, mainly across central areas, remaining largely dry elsewhere. Strong winds throughout, and feeling very cold, with ice and widespread frost developing. Minimum temperature -3 °C.
Tuesday:
Another day of continued snow showers, primarily across northern and central areas, possibly reaching further west than Monday, with intermittent dry spells. Strong winds, feeling very cold. Maximum temperature 3 °C.
Outlook for Wednesday to Friday:
Sunny spells and scattered snow showers on Wednesday. Showers ease on Thursday leaving drier conditions. Widespread rain and snow expected on Friday. Remaining very cold with brisk easterly winds.
