Temperatures soared to 21C today as the country basked in the warmest March day for five years.
See also: Britain's wettest cities revealed
See also: Temperatures to soar to 22C - but will the sunshine last?
But the Met Office has warned that heavy and persistent rain will be seen across the UK on Saturday, "bang on queue".
It's set to be a rainy day tomorrow in central England and northern Scotland, with temperatures in single figures.
Conditions will continue to be "unsettled" on Saturday, particularly in the west, forecasters have warned.
By Saturday afternoon, showers could be heavy with a risk of thunder
April showers to hit the UK 'bang on queue' warn the Met Office
Sunday should be a drier day with temperatures in double figures
"The rain will move across the country by Saturday afternoon and we will see hefty showers, widely across the UK with heavy downpours and a risk of thunder and hail," a Met spokesman said.
This will die down overnight, and Sunday should be a much clearer day with "fine weather," high pressure building, longer spells of sunshine and temperatures feeling warmer again.
Most of London and the south east enjoyed a warm and sunny day today.
The warmest temperature was in the 'Garden of England' with 21.8C (71.2F) recorded in Gravesend, Kent.
Other parts of the country were warmer than holiday hotspot Ibiza which only reached a high of 18.8C (66F).
Parts of Britain enjoyed temperatures of 21C today
Britons enjoyed a warm spring day today but it might not last long
The country basked in the warmest March day for five years on Thursday
But forecasters warned the unseasonably warm temperatures and sunny weather are not due to last into the weekend, with experts forecasting some cloudy weather and highs of 18C (64.4F).
Met Office forecaster Nicola Maxey said: "We've reached 21.8C in Gravesend which is the highest March temperature for the last five years.
"It is all thanks to some warm air coming up from the continent which is bringing the warmer spell of weather, but it's just for today."
She said the average temperature for March as whole for the UK was 9C (48.2F).
Ms Maxey added: "Obviously you would expect to see below average temperatures at the start of the month and above average at the end because you are moving your way though the year from one season to another.
"You would expect temperatures to get warmer as you go. The average temperature for April for the whole UK is 11C, so we are quite a bit above average for the time of year."
The highest temperature ever recorded for the month was 25.6C on March 29, 1968, in Mepal, Cambridgeshire.
The Met Office said today was the warmest March day we've had in five years
Looking ahead to the weekend, she said: "Tomorrow temperatures will be dropping back down to the mid-teens, but this is still quite high for the time of year, say around 17 or 18C for the London and south east area.
"Friday will be a good day for most of England and Wales with sunny spells around but there is some rain moving north, over Northern Ireland and Scotland.
"Then as we go into the weekend there will still be those sunny spells, but there will be some fairly heavy showers which will feature quite widely across the country for the day.
"Some of those could be quite heavy and there could be some thunder and some hail. But they are showers, so in between them there will be those sunny spells."
She said some of the showers could be quite heavy, and that temperatures will be a bit colder again in the mid teens, but still above average for the time of year.
April showers are set to hit the country this weekend
Heavy rain will be seen in some parts of the UK on Saturday
She added: "Sunday will probably be the best day of the weekend with plenty of bright sunny spells and again temperatures just above average."
"Even with the drop in temperature over the weekend from the high of Thursday, things will still be well above average and you'll still have good weather."
When asked about the weather for annual Oxford and Cambridge Boat Race on the River Thames in London, she said: "Well things will be pleasant for the race.
"There will be fairly gentle breeze, with 3mph to 4mph winds with gusts getting up to 10mph , but nothing too onerous I wouldn't have thought."