Weather maps predict exact date 600-mile wall of rain to drench UK

Brits are set to be dealt meterological whiplash this week as a 600-mile wall of water replaces the UK's fourth heatwave, bringing inches of rainfalll to some parts of the country.

Extreme heat has scoured the earth across every home nation over the last week, with the mercury tipping into the 30C once again in what appeared to be a mid-August last summer hurrah. Temperatures have slid back down over the weekend, ahead of what weather maps predict will be a major washout.

The new maps from WXCharts show that only a handful of areas won't see rain as the weather system hits in a matter of days, clearing the way for what the Met Office warns will be "rather cool" conditions.

READ MORE: Horror weather maps show when 600-mile rainstorm will batter UK - 8 counties will avoid

WXCharts rain overview maps show the system blowing in from the west towards the end of this month, landing over the coast by August 27.

The maps show rainfall totals reaching general concentrations of between 1cm to 2cm in most areas, with accumulation maps suggesting that some totals could build as high as 18cm (seven inches) over high ground in southern central Wales.

The maps indicate that only eight areas will miss out on the deluge, including Aberdeenshire, Somerset, Middlesex, Kent, Essex, Suffolk, Norfolk and Cambridgeshire.

While the rainfall will arrive and depart in a flash, it looks likely to return again just a few days later on September 1, and with more of a bang, with the same accumulation maps predicting that up to 31cm of water (12 inches) could pelt high ground in northern Wales. The entire period - from August 21 to 30 - will also be colder, the Met Office predicts.

The long-range forecast from the agency states that high pressure from Iceland will drift south over the next week, bringing "rather cool conditions", with the rain likely forming as a remnant of Tropical Storm Erin.

It states: "High pressure is likely to be the dominant feature at first, initially centred near to Iceland, allowing a north to northeasterly airstream to affect much of the UK, leading to rather cool conditions.

"High pressure is likely to progress SE across the UK for a time, bringing widely fine and dry conditions and for some, an increase in temperatures, relative to the previous few days.

"Whilst this is happening a deep area of low pressure is likely to develop in the North Atlantic, linked to Tropical Storm Erin. The final week of August may see Atlantic weather systems progress over the UK, especially in the north and west, with a small chance of widely wetter and windier weather developing. The evolution of this is highly uncertain though."