Monday could be one of the warmest days of the year so far with spring just over a week away.
Southerners will see a mild start to the week, with the mercury peaking in the late teens, the Met Office said.
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The warm spell will follow a chilly night for parts of the UK, with an overnight frost affecting parts of northern England, Wales, the Midlands and South West.
Forecaster Marco Petagna said: "We're looking tomorrow (Monday) at around 16C (61F), with about a 30% chance of getting to 17 or 18C (62-64F) somewhere in the South or South East.
"Even that's just a little bit shy of this year's record, but certainly warm."
Temperatures will have to soar higher than the 18.3C (65F) recorded on February 20 in Northolt, north-west London, and Kew Gardens, south-west London to become the hottest day of 2017.
While it will be dry and reasonably sunny in the South and South East of the country, towards the North and North West there will be more cloud and the chance of drizzle for the first half of the week.
On Tuesday there could be gales in North and north-west Scotland, with gusts of up to 60 mph.
Towards the end of the week temperatures will fall but remain just above the average maximum highs for mid March - 8 or 9C (46-48F) in the North and between 9 and 11C (48-52F) in the South.
But Mr Petagna quashed hopes that it could be the hottest March week ever, as thousands of race-goers prepare to descend on Cheltenham.
The forecaster said it was unlikely that the mercury will reach 25.6C (78F) - the highest ever March temperature recorded on March 29 in 1968 in Mepal, Cambridgeshire.
Race-goers can expect a "fair bit of cloud" but will enjoy largely dry conditions, he said.