“There will be a touch of frost around and some of the showers for northern Scotland will be sleety”
The Met Office said it would be a “week of two halves” with sleet and heavy downpours wreaking havoc until the tail end of the week.
From Thursday onwards temperatures are expected to rise with the mercury reaching a high of 23 and 24C this weekend.
Meteorologist Aidan McGivern said: “It will be cool at first and then later in the week it’s going to warm up considerably.
“Look at the contrast for the end of the week the jet stream pushes north again bringing these warmer colours especially to southern Britain and bringing a return to some sunshine.
“However on its journey northwards that jet stream will bring lashings of rainfall especially over the hill of western Britain, from Wales northwards.”
He added: “On Tuesday there will be a touch of frost around and some of the showers for northern Scotland will be sleety with snow over the Scottish mountains.
“But, for western Scotland, Northern Ireland and later in the day for Wales, and the southwest the showers ease away to bring plenty of sunshine.”
The wetter conditions earlier in the week will be due to a jet stream which is moving across the south of the UK, bringing showers in its wake.
Mr Aidan said conditions would start to dry up by Thursday across the south, although it would still be wet in western Scotland, Northern Ireland and western hills of northwest England and Wales.
He continued: “As we head into Friday with temperatures on the rise day-by-day.
“On Saturday and Sunday temperatures will climb into the mid or even high 20s, so a very warm weekend to come.”