Forecasters have warned of treacherous driving conditions and travel disruption, with localised flooding in parts of southern England, Wales and Northern Ireland and up to 12cm of snow forecast across parts of northern England and southern Scotland.
Temperatures dipped as low as minus 7C (19.4F) in the Scottish Highlands overnight while torrential rain moved in from the south and west amid milder conditions.
Most of Wales, England and Northern Ireland is covered by a yellow warning for heavy rain, with up to 70mm expected to fall in some areas.
Around 150 flood alerts and 15 flood warnings were in place across England on Monday morning.
Meanwhile much of northern England and southern and central Scotland is covered by snow warnings.
There were concerns that some rural communities could become cut off, mainly across the northern Pennines and Scottish Borders, with “significant accumulations” of snow forecast.
The Met Office said there is a chance of delays on roads, with some stranded vehicles and disruption to rail and air travel.
Forecaster Marco Petagna said: “With this rainfall we are certainly looking at some localised flooding in south-west England, Wales and Northern Ireland anywhere in the warning area.
“In terms of snow there could be travel problems on some Pennine routes and higher ground.”
For those who are travelling across Britain, warnings have been issued that train services could be disrupted and heavy traffic will take to the roads.
The AA warned motorists to take extra care and said the bank holiday weekend is “likely to be one of the busiest on the roads in recent years”.
It is not unusual weather in the UK in April - the month sees an average of 2.3 snow days each year.