Highest temperatures are expected to lie between 15° and 20° in the midlands and east of the country.
This is expected to cause many major routes to be clogged, with the worst delays between 11am and 4.30pm.
Easter Sunday will stay largely dry over the weekend and into Easter Monday, with bright or sunny spells.
Tenby, a holiday destination in South-East Wales, will be cooler - as will the rest of Wales - with temperatures reaching highs of 15C (59F).
Scattered rain showers will be possible throughout the day, with morning temperatures starting off around 54 degrees, and cooling into the upper 40s Friday afternoon.
On Friday, showers will be likely all day, with a breeze attached.
"Temperatures will reach into the low 20s Celsius quite widely and there's a good chance some places particularly in the south could see temperatures peaking around 24 to 25 Celsius".
The good weather means people are being warned of traffic jams as millions plan to set out for the bank holiday. Those in Manchester and London will bask in 23C. Edinburgh will be markedly cooler at around 16C.More news: U.S. health officials seek to stem measles outbreaks traced to Israel, Ukraine
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While double digits are in the forecast, rain is expected from Thursday through Sunday.
"On Sunday there will be more clouds and rain pushing in across Scotland and the far north of England", said Mr Burkill. Mostly sunny, with a high near 65.
The west and midlands promise the best bets for bouts of hazy sunshine and temperatures nudging 21C or 22C today.
The reason why the clouds and precipitation are going to last for so long is because the jet stream will take on a configuration parallel to the weather system itself.
"The average temperature for April is around 11 to 12 degrees, so it is definitely warmer than we might expect for this time of year", Ms Diamond said.
"The weather will be a bit more changeable and unsettled".
Along with the rain, gusty winds could snap tree branches and bring some trees down.