Boris Johnson has told MPs he will chair a Cobra crisis meeting on Wednesday as Storm Christoph brings “significant” rainfall across large swathes of the UK.

Communities are bracing for flooding and major incidents have already been declared in Greater Manchester and South Yorkshire amid amber and yellow weather warnings for the storm, which could also bring snow to northern areas.

More than 120mm of rain has already fallen in parts of the country, with 123.4mm at Honister Pass in Cumbria in the 24 hours up to 6am on Wednesday.

Nearby Seathwaite saw the second highest total, with 107.2mm, and some isolated spots could see up to 200mm, the Met Office said.

Fifty-one warnings have been issued by the Environment Agency across England, with 179 less severe flood alerts, mainly across the Midlands and north of the country.

Speaking during Prime Minister’s Questions on Wednesday, Boris Johnson told MPs: “Our sympathies also go out to those affected by the latest floods.

“I want to thank the Environment Agency and our emergency services for the work they’re doing to support those communities, and I’ll be chairing a Cobra meeting later on to co-ordinate the national response.”

Almost the whole of England, Wales, and Northern Ireland are subject to yellow weather warnings for rain until midday on Thursday, with a more serious amber warning stretching from the East Midlands to the Lake District.

The amber alert warns of the risk of flooding and deep floodwaters which could pose a risk to life, and there are further yellow warnings for snow and ice in Scotland.

Met Office forecaster Grahame Madge described Christoph as “quite a slow-moving system” which is bringing “a variety of weather” to the UK.

The meteorologist said: “While rain remains the main hazard in the south, further north we’ve got snow and ice remaining a risk.

“The system will work its way through, we are expecting significant totals of rainfall and when you combine that with snowmelt it can lead to localised flooding across the affected regions.”

South Yorkshire declared a major incident on Monday evening in anticipation of flooding, and Greater Manchester Police followed suit on Tuesday.

The force said people should leave flooded homes if instructed, despite the stay-at-home messaging of the pandemic.

Assistant Chief Constable Nick Bailey said: “Coronavirus remains a threat to everyone’s health and people should not leave their homes unless it is absolutely essential, but where there is a risk of flooding, that is clearly essential and we’re working with our partners to ensure that people can do this as safely as possible.”

Rail services have been disrupted on the Northern network after tracks flooded.

There are suspensions on services from Carlisle to Skipton or Maryport, all destinations from Rotherham Central, and between Manchester and Newton le Willows.

Trains are also subject to disruption between Leeds and Manchester, Salford Crescent to Preston and another of other routes.

A spokesman for Northern said: “The difficult conditions are being experienced across a large part of our network and customers planning to travel today should be aware that any journeys could be affected and they should allow extra time for travel.”

People were also preparing for rising floodwaters in West Yorkshire on Wednesday morning, with towns in the Calder Valley laying out sandbags and flood wardens monitoring water levels.

As the week continues and Storm Christoph makes its way east, the risks of snow increase, Mr Madge said.

“When Christoph starts to move into the North Sea we will start to see more northerly influence coming in, we’re going to have a feed of colder air which will bring in wintry showers,” he said.

“Over higher ground to begin with but increasingly those events will be to lower levels as well and that could lead to some accumulations in Scotland, northern England and parts of Northern Ireland.”