Rail workers will walk out for a second day, while Royal Mail employees and driving examiners are also striking.
Tuesday's walkout by rail staff left services running at about a fifth of capacity, on a day when snow, ice and fog hampered road and air travel.
Around half of rail lines will be shut again on Wednesday, with no services at all in most of Scotland and Wales.
The first-ever nationwide strike by nurses is also expected to go ahead this week.
And on Friday, rail workers, buses, baggage handlers, highway workers and driving examiners will walk out.
The government's emergency Cobra committee will hold its second meeting of the week later to discuss how to minimise the impact of the wave of industrial action.
One small business in Brighton which relies on Royal Mail to get its products to customers said the strikes in the run-up to Christmas were "frustrating".
Lucy Bryant, who runs her artist's studio, Haus of Lucy, says she supports the strikers as "everyone has a right to fair pay".
However, she relies "so heavily on the post" to get products from suppliers and to send her art to customers that she says the Royal Mail strikes "have made my life very hard this Christmas season".
"I've got the frustration of my customers to deal with," when artworks don't arrive on time in the run-up to Christmas, she says. "It's frustrating for them, and it's frustrating for me."
Some artworks are getting through, and some aren't. "There's almost no logic to what is getting through," she says.
Lucy had to re-order prints that didn't arrive at a cost to the business "that is quite a big hit for me to take," she says.
"I'm not Banksy - yet," she adds.
Lucy says using other postal service providers "is a bit of a wild west", but if strikes continue, she may be forced to find alternatives to Royal Mail, which is a service she trusts.
On Wednesday, the Office for National Statistics will announce the inflation figure for November. In October, that rate was 11.1%.
On Tuesday, figures from the ONS revealed that the gap between wage growth in the public and private sector is near a record high.
The average pay rise for workers in the private sector was 6.9% between August and October. That compares to wage growth of just 2.7% for public sector employees.
A spokesman for Royal Mail said the company had made a "best and final pay offer worth up to 9% over 18 months".
"Instead of working with us to agree on changes required to fund that offer and get pay into our posties' pockets, the CWU has announced plans to ballot in the New Year for further strike action."
But a spokesman for the CWU said that Royal Mail has offered workers a 3% pay rise this year, 3% next year as well as an additional 2% if employees agree to "the absolute destruction" of terms and conditions.
Along with the rail industrial action on Tuesday and Wednesday, there will also be train strikes on Friday and Saturday.
This is part of a long-running dispute between unions, rail firms, the government and Network Rail over pay, job cuts and changes to terms and conditions.
Employees are being squeezed by the rising cost of living, and want pay deals that reflect this.
But the rail industry was hit by a drop-off in passenger numbers during the Covid pandemic, and it's under pressure to save money. Bosses say reforms need to be agreed, to afford pay increases and modernise the railway.
Network Rail wants to cut 1,900 jobs as part of changes to the way its maintenance teams work - although it insists most of this could be achieved by people leaving voluntarily.
The RMT disagrees with some of the changes and wants a guarantee of no compulsory job losses.