After cold air surged into Wales at the end of the weekend, forecasters are warning residents the chill won't be quick to retreat.
Overnight on Sunday into Monday, the Met Office recorded the lowest temperature in Wales since early this year.
Sennybridge in Powys fell to an icy -6C just before 4am on Monday, the coldest reading in the country since January 31.
Over the next few days, minimum temperatures will rebound slightly, but those heading outdoors will notice significantly chillier air during the daytime.
"Following what was an exceptional autumn for many parts of England and Wales, December has started with quite different weather patterns," Aidan McGivern of the Met Office said.
"Finally a prolonged spell of dry weather, and that continues over the next few days with frosty and foggy mornings.
"But in the north, more blustery conditions start to evolve in the week ahead and those blustery conditions spread to all parts by the end of the week," he said.
Most of Wales will see minimum temperatures in the low single digits overnight.
Swansea will see minimum readings drop to around -1C into the middle of the week, climbing only slightly as the day progresses.
While sun will peek out from behind the cloud during the afternoon, maximum temperatures will fail to exceed 8C or 9C.
Areas further north will face the same numbing conditions.
Rhyl is forecast to hover around 3C overnight for much of the week, with highs around 8C through to at least Wednesday.
Across the whole of the country, those heading out early for the morning commute should be prepared for dense and freezing fog.
This could lead to reduced visibility, resulting in speed restrictions on major routes.
Motorists will also want to keep ice scrapers to hand as windscreens promise to be glazed over during the early morning hours.
By the weekend, a final widespread frost is expected before strong winds and rain sweep in from the west.
Here's what to expect where you live:
Cardiff
Swansea
Tenby
Aberporth
Aberystwyth
Porthmadog
Rhyl
Builth Wells
