Scotland, in particular, is expected to see a large amount of downpour, as well as Northern Ireland, and parts of northeast England. A rain warning, which was first issued on Sunday evening, remains in place for southwest Scotland.
Meanwhile low pressure will see “strong, gusty” wind, which started overnight and will carry on throughout much of the day, affect parts of Scotland. In England, the wind will travel in a northerly direction – hitting Plymouth first, then Cardiff, Birmingham and Manchester before dissipating.
There will be some sunny spells in southwest England but the wind will mean temperatures do not exceed around 14C. In Newcastle, there will be lows of 9C.
The Met Office has called this week’s weather “unsettled”, making reference to the north/south divide in this week’s forecast which will continue to chop and change over the coming days.
On Monday alone, there were lows of 2C in Herefordshire, in the Midlands, while Kew Gardens, in London, saw highs of almost 17C.
Tuesday evening will be mostly dry with bright spells and scattered showers across Wales and western England, which will likely be locally heavy before turning increasingly light and patchy, according to the PA news agency.
Overnight, rain will continue across Scotland and spread into southern Britain by dawn.
By Thursday, though, the Met predicts a u-turn – while the northwest will experience extended periods of sunshine, rain and cloud will leave eastern and southern parts of the UK cold and wet.
Worsening conditions in southern England are, in part, due to the European storm – named Storm Barbara by Spanish meteorologists – which is due to strike Spain and Portugal from today. Some areas on the Iberian peninsula are set to see the equivalent of four to six weeks’ worth of rain in just a few days.
But British forecasters have said the storm won’t have any “major impacts” on the UK, highlighting that no weather warnings have been issued across Britain.
Met Office spokesman Oli Claydon told the PA news agency: “It's not a storm that's had any naming influence from us ... we haven't got any warnings out.
“But it will bring some some wind and rain to parts of the UK, particularly in the south tomorrow.
“From this evening, into the early hours, there will be a band of rain moving in from the South, bringing some at times heavy rain, particularly in the southeast, and then following that later in the day, a period of stronger winds, particularly again in the southeast.”