A mini heatwave could enable the UK to break its record March temperature of 25.6C (78F) next week.
A southerly air flow will bring conditions similar to those in southwest France and southern Spain on Monday and Tuesday.
Temperatures are forecast to get very close to the record figure, set in Mepal, Cambridgeshire, in 1968.
London is most likely to see such unseasonal March conditions, along with areas just north of the capital.
The warmth will be relatively widespread, however, with temperatures reaching the early 20s Celsius for many parts of England and Wales.
And although parts of the north will be wet, temperatures will be higher than average there too.
That will especially be the case on Monday for eastern parts of Scotland, where temperatures could locally be up into the upper teens.
Average maximum temperatures for the end of March in the UK and Ireland are around 12C (53F) in the south and 8C (46F) in the north.
The Easter weekend is looking much chillier, however, as a significantly colder air mass is due to sweep southwards mid-week.
While the holiday weekend is looking mostly fine and settled thanks to high pressure, some places will experience wintry showers.
This coming weekend will also be disappointing for some, with blustery showers turning increasingly wintry.
On Friday there will be sleet and snow, mostly over the high ground of northern and western parts of the UK and Ireland, but into the night there may be slight accumulations on low levels too.
Around 1cm to 3cm is possible at elevations of 150m to 200m across parts of Scotland, Ireland, Northern Ireland, northwest England and Wales. There will also be a risk of ice, as well as a widespread frost.
Saturday will see showers easing through the morning, leading to a mainly dry and bright day, before cloud and rain spread to northern and western areas.