Heavy rain is battering parts of southern England and Wales on Thursday 18 December as the Met Office’s yellow weather warnings come into force, capping off a very wet spell that forecasters say heightens the risk of disruption to travel and localised flooding.

With saturated ground across large areas and further bands of intense rainfall sweeping in from the southwest, transport operators are urging passengers to check before they travel and to prepare for delays and cancellations through the evening.

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Met Office issues yellow rain warnings after prolonged wet spell

The Met Office has placed yellow rain warnings across much of south Wales, southwest England and southern counties of England through Thursday 18 December, warning that heavy and persistent downpours could cause disruption to road, rail and bus networks.

Forecasters say many locations within the warning areas are likely to see 15 to 25 millimetres of rain, with 40 to 60 millimetres possible over higher ground such as Dartmoor, the hills of south Wales and the Downs.

The alerts follow a sequence of unsettled days driven by a series of low pressure systems, which have already brought repeated bouts of heavy rain, brisk winds and local flooding to parts of the UK this week.

The Met Office has underlined that the greatest impacts on Thursday are expected where the new rain falls on already saturated ground, particularly across southern England and south Wales, increasing surface water and river levels.

In a briefing issued on Wednesday 17 December, the Met Office highlighted that a waving frontal system would move in from the southwest, bringing another spell of heavy rain and blustery winds to the same southern regions that have borne the brunt of recent downpours.

Strong coastal gusts of 50 miles per hour or more are expected to accompany the rain along parts of the English Channel and Bristol Channel coasts, adding to the hazards for road and rail travel.

Met Office chief forecasters have stressed that while the warnings in place are at the yellow level, the impacts could still be significant in localised hotspots, especially where drainage is already struggling to cope. They are advising the public to stay weather aware, keep up to date with the latest warnings, and avoid driving through floodwater under any circumstances.

Where the heaviest rain is expected in southern England and Wales

The most intense rainfall on Thursday is expected to focus on a broad swathe extending from Cornwall and Devon through south Wales and into southern and southeastern England.

High ground in the southwest and south Wales is particularly prone to heavier accumulations, with orographic uplift enhancing the rainfall totals over hills and moors. In these areas, forecasters say 40 to 60 millimetres of rain is a realistic prospect during the course of the day.

In Cornwall, a local yellow warning for rain, valid from late morning into the evening, highlights the risk of difficult driving conditions, spray and localised flooding on key roads.

Regional forecasters warn that a band of heavy rain will move across the county through the day before clearing eastwards later, with the potential for standing water to build quickly on rural routes and low-lying stretches of the A30 and A38. Similar concerns apply across Devon and into Somerset, where many minor roads are already holding water from earlier weather systems.

Across south Wales, including parts of the Valleys and coastal communities, Thursday’s warning window runs from mid-morning into the evening. The Met Office has cautioned that much of the area can expect 15 to 25 millimetres of rain, with pockets of 40 to 50 millimetres where showers band together or stall over the high ground.

With rivers and streams still elevated after previous heavy falls, there is a heightened risk that even moderate additional rain could push some watercourses close to or above bankfull.

Further east, a separate yellow rain warning is in force for southern counties of England, taking in stretches of the south coast and parts of the southeast. Within this zone, rainfall totals are forecast to reach 15 to 25 millimetres quite widely, with up to 60 millimetres possible over the Downs.

While the southeast has not been as consistently wet as the southwest in recent days, localised surface water problems are still anticipated in urban areas where drainage networks can be overwhelmed by intense bursts of rain.

Rail and road networks brace for disruption through the evening peak

Rail operators serving southern England and Wales warned on Thursday afternoon that services were being affected by the deteriorating weather, with passengers urged to allow extra time and to check for last minute changes before setting out.

CrossCountry and South Western Railway both issued updates highlighting the impact of heavy rain across wide areas of their networks, citing the Met Office’s yellow weather warnings for heavy rainfall as a key factor.

According to passenger information systems, services on numerous routes were subject to delays and short-notice cancellations as reduced speeds were imposed in areas of poor visibility and reports of flooding on the line filtered through.

Some trains were diverted away from low-lying sections vulnerable to inundation, while others were cancelled outright where water levels made sections of track temporarily unsafe.

On the roads, National Highways and local councils reported spray, standing water and slower traffic on several key routes through the afternoon, particularly on exposed stretches of motorway and dual carriageways in southern England.

Commuters faced difficult driving conditions in heavy rain, with glare from headlights and reduced visibility adding to the usual evening peak congestion. Police and motoring organisations advised drivers to lower their speed, increase stopping distances and ensure headlights were switched on in reduced visibility.

In rural parts of south Wales and southwest England, smaller B roads and lanes were among the first to report problems as drainage ditches filled and water spilled across carriageways.

Some communities that experienced flooding earlier in the week prepared for renewed disruption, with sandbags and temporary barriers still in place outside homes and businesses that had been affected by surface water and overflowing streams.

Communities still recovering from recent flooding face renewed risk

The latest warnings arrive just days after serious flooding impacted communities in parts of south Wales, leaving some households facing extensive damage to homes and possessions in the run-up to Christmas.

Images from affected areas showed streets turned into rivers, cars partially submerged and residents using buckets and pumps to remove water from living rooms and kitchens. In some streets, festive decorations and gifts were left waterlogged as floodwaters rose more quickly than expected.

For residents still cleaning up from earlier inundations, the prospect of more heavy rain is a significant concern. Local councils and emergency services across Wales and southwest England have maintained heightened readiness, with teams monitoring river levels and surface water hotspots, and checking that temporary defenses remain effective where they are still needed.

Volunteer groups and community organisations have also been supporting vulnerable residents, particularly older people and those with mobility issues who may struggle to move belongings or evacuate quickly.

The Environment Agency and its Welsh counterpart have kept numerous flood alerts and warnings in place over the past week, reflecting the lingering sensitivity of rivers and catchments after prolonged rainfall.

With soils at or near saturation point across many western areas, any additional rain runs off quickly into watercourses, accelerating rises in river levels and increasing the likelihood of both flash flooding and more gradual fluvial events.

In some low-lying districts, local authorities have warned there is a small chance that fast flowing or deep floodwater could pose a danger to life, particularly where people attempt to drive through flooded roads or become trapped in rapidly rising water.

Emergency planners are reiterating that even apparently shallow water can conceal hazards such as lifted manhole covers, debris or deep potholes that may catch pedestrians and vehicles unawares.

Travel advice for passengers and motorists navigating the deluge

As the yellow rain warnings remain in force through Thursday, travel and safety agencies are issuing practical advice for those who have to be on the move. Rail passengers are being encouraged to check live departure boards and operator websites before traveling, as timetables may change at short notice in response to localised flooding, signal failures or speed restrictions.

Where possible, travellers are urged to consider earlier services to avoid the worst of the evening weather, or to work flexibly if their employer allows.

Motorists are being advised to take particular care on unfamiliar rural roads, where standing water can appear without warning around bends or in dips. Road safety campaigns underline that as little as 30 centimetres of moving water can float a car, and that it takes only a small quantity of water entering the engine to cause severe and costly damage.

Drivers are being told that if they encounter a flooded road, the safest choice is to turn around and find an alternative route rather than attempting to gauge the depth.

For those living or staying in at-risk areas, including holidaymakers visiting the southwest and south Wales in the run-up to Christmas, authorities recommend preparing a simple flood plan.

This may include moving valuables and important documents upstairs, charging mobile phones, identifying safe exit routes from the property and checking in on neighbours who may need assistance. People are also urged to keep an eye on local news and official weather updates, as conditions can change rapidly when frontal systems become slow moving.

Air and ferry passengers heading to or from southern UK ports are also being told to monitor their carriers’ latest travel information. While the current warnings are focused on rain rather than wind alone, gusty conditions near coasts and potential congestion on road and rail approaches to airports and ferry terminals mean journey times could be extended, with knock-on effects for check in and boarding.

Outlook: a drier and cooler turn into Christmas week

Despite the difficult conditions on Thursday, there are tentative signs that the UK’s weather pattern may shift as Christmas approaches. A recent Met Office 10 day outlook suggests that after this midweek burst of wet and windy weather, pressure is likely to build over or near the UK, bringing a spell of quieter, drier and somewhat cooler conditions for many areas into Christmas week.

Forecasters caution, however, that details remain uncertain, and that showers and further rain bands cannot be ruled out entirely, especially for northwestern parts of the country. For those in southern England and Wales who have borne the brunt of this week’s rain, any sustained drier spell would help river levels to ease and allow saturated ground to begin drying, reducing the risk of additional flooding from subsequent weather systems.

In the shorter term, Friday and the weekend are expected to bring a mix of blustery showers and brighter intervals, more typical of the season after the more organised bands of heavy rain clear away.

Temperatures are likely to trend a little lower but remain around or slightly above the late December average for many southern areas, meaning that concerns about snow and ice are secondary to the immediate issues posed by rainfall and localised flooding.

With Christmas travel due to ramp up over the coming days, transport operators and meteorologists alike will be watching incoming charts closely. If high pressure does establish itself as expected, it could provide a more benign backdrop for the busiest getaway days, but fog, frost and patchy rain are still possible complications for drivers and rail users even in a quieter pattern.

FAQ

Q1: Which areas are covered by the Met Office yellow rain warnings on Thursday 18 December?
Southern England and south Wales are the main focus, including parts of Cornwall, Devon, Somerset, the south coast counties and southern Wales, with separate warning zones for southwest England, south Wales and southern counties of England.

Q2: How much rain is expected during this warning period?
Many places within the warning areas are forecast to see 15 to 25 millimetres of rain, with higher totals of 40 to 60 millimetres possible over hills and upland areas such as Dartmoor, the hills of south Wales and the Downs.

Q3: Why is the risk of flooding higher after this recent wet spell?
Because the ground is already saturated from previous heavy rain, it cannot absorb much more water. This means additional rainfall runs quickly into rivers, streams and drains, increasing the likelihood of surface water flooding and rapid rises in river levels.

Q4: How are train services being affected in southern England and Wales?
Operators including CrossCountry and South Western Railway have warned of delays and cancellations on parts of their networks, as heavy rain leads to speed restrictions, potential flooding of track and occasional route closures, particularly on low lying or rural sections.

Q5: What should drivers do if they encounter a flooded road?
Authorities advise drivers not to attempt to drive through floodwater. Even apparently shallow water can hide hazards and as little as 30 centimetres of moving water can float a car, so the safest option is to turn around and find another route.

Q6: Are homes and businesses at risk from this latest band of rain?
Yes, there is a chance that some properties, especially in low lying or previously flooded areas, could experience water ingress if drains and rivers are overwhelmed again. Local agencies have warned that some communities may face renewed disruption where defences are already under strain.

Q7: Will the weather improve in time for the main Christmas travel period?
Current Met Office guidance suggests a trend towards drier and somewhat cooler conditions into Christmas week as high pressure builds, which should ease the risk of widespread heavy rain, although local showers, fog and frost could still affect travel.

Q8: What precautions can residents in at risk areas take today?
Residents are encouraged to move valuables upstairs, prepare a simple flood plan, keep phones charged, monitor local forecasts and alerts, and check on neighbours who may need help, particularly older or less mobile people.

Q9: How long are Thursday’s yellow rain warnings expected to last?
The warnings in place for south Wales and parts of southwest and southern England generally cover the daytime and early evening period on Thursday 18 December, with the heaviest rain expected from late morning into the afternoon before clearing eastwards later.

Q10: Are flights and ferries likely to be disrupted by this weather?
While the main hazard is heavy rain rather than extreme wind, strong coastal gusts and difficult road and rail conditions around airports and ports could lengthen journey times and cause some schedule changes, so passengers are advised to check with their carriers before traveling.