Motorists are being warned to stay off the roads as cars have become stuck in flood water caused by downpours and the UK prepares to suffer “miserable conditions” over the next two days.

The Met Office issued weather alerts as a band of rain, which arrived in Cornwall on Wednesday afternoon, travels across the country before passing over Scotland’s east coast on Friday.

Conditions may be “atrocious” for much of the UK, while the Scottish highlands could see some snow, the forecaster said as it put out a yellow warning for rain.

In West Sussex, the A27 was closed in both directions between Emsworth and Chichester following heavy rain – which left up to 20 cars stuck in flood water, according to West Sussex Fire and Rescue Service.

The service posted on Twitter: “Police on the scene and the road closed in both directions. We are attending with specialist equipment to help bring people to safety. AVOID THE AREA and only travel if necessary.”

Some rail lines were impacted on Wednesday night and Thursday morning, with disruption between Tonbridge and Hasting caused by flooding in a tunnel at Wadhurst in East Sussex.

National Rail said it had rectified a fault in the tunnel involving a blown fuse and a melted piece of signalling equipment, with disruption on the line until at least 6am.

Flooding between Lewes and Brighton stations is also causing disruption expected until 9am, including cancellations and delays.

On the Isle of Wight, flooding has caused the cancellation of trains on the Island Line until 9am.

And motorists were being warned by travel service Romanse of “heavy delays” around the A27 and A3M near Havant, Hampshire, because of flooding caused by the rain.

Police in Winchester, Hampshire, have also advised of a large tree coming down and blocking a road in Swanmore.

Meanwhile, the Environment Agency had issued three flood warnings and 43 flood alerts mostly across the south coast as of Wednesday afternoon.

The Met Office’s first weather warning kicked in at 5pm, covering a southeast area stretching from Southampton and the Isle of Wight in Hampshire to the coast in Kent, until 6am on Thursday.

Forecasters warned roads, homes and businesses could be flooded and transport services disrupted.

Another yellow rain warning then came into force across a large area of the UK for the whole of Thursday, from 12am until 11.59pm.

This covers an area stretching from Birmingham, Lincoln and Hull to north Wales, Liverpool and Manchester, as well as the east coast up to the Scottish border.

The rain brings a small chance of homes and businesses flooding, communities being temporarily cut off by flooded roads and disruptions to transport, the Met Office warns.

A third warning will come into force at 3pm on Thursday until 6pm on Friday for the east coast of Scotland, stretching from the English border up past Aberdeen with similar risks of flooding and transport disruptions.

A yellow weather warning was also issued for fog across parts of Northern Ireland from 4.40am to 10am on Thursday.

Met Office spokesperson Craig Snell said: “The warning areas are where we are most concerned about the risk of flooding but it doesn’t mean that the areas outside them are not going to see some pretty atrocious conditions.”

Mr Snell said a warning is in place for the southeast because “it has been quite wet there since the beginning of November with many places already seeing more than their month’s share of rain”.

The midlands and the north of England will have a “pretty miserable day” on Thursday after the rain sweeps in overnight, Mr Snell said.

“The rain will be accompanied by a brisk wind so it’s not going to feel good.”

But he added Scotland could see “two days of persistent rain” and this may result in snow falling in the highlands – although this is not unusual for November.

“If you want to take a walk in the hills in Scotland tomorrow you may come across snow but for the lower levels it is just going to be rain,” he said.

RAC breakdown spokesman Rod Dennis warned motorists to “exercise great care” during the wet weather.

“The chances of being involved in a collision rise dramatically in wet weather, and even more so if there’s snow, so it’s vital drivers slow down, leave plenty of space behind the vehicle in front and use their lights to make sure they’re easily seen by other road users,” he said.

“The risk of aquaplaning where a vehicle’s wheels lose contact with the road as they skim across standing water will be high, particularly for those who don’t slow down to appropriate speeds for the conditions.”