The Association of Train Operating Companies (Atoc) anticipated about 6.5 million rail journeys will be made over the bank holiday weekend.
An Atoc spokesman said: "The vast majority of people travelling by train this bank holiday will be unaffected by improvement work."
Channel Tunnel high-speed train company Eurostar said it expected to handle more than 120,000 passengers over the weekend - 10% more than over the Diamond Jubilee bank holiday period last year which was the first weekend in June.
Tomorrow will be Eurostar's busiest day of the holiday period.
Bosses at Gatwick said more than 790,000 passengers would be passing through the West Sussex airport between bank holiday Monday and Sunday June 2.
Among popular destinations for those flying from Gatwick are Spain, Portugal, the Balearic Islands, Turkey and the south of France.
Top city breaks include Dublin, Belfast and Amsterdam.
Eurostar services from St. Pancras are still suffering problems because of wintry weather conditions in northern France and Belgium. The company has cancelled some trains and others could be delayed by up to two hours. They also say that the amended service will continue tomorrow.
They are asking customers who do not have a confirmed ticket for a train that is running to stay away from their stations. Details of the services which are running can be found on the Eurostar website.
Eurostar has said that it expects to run an amended service tomorrow after bad weather in France and Belgium meant its trains has to be cancelled today. Journey times tomorrow will be between 40 and 60 minutes longer than usual.
There are delays of up to one hour on the Eurostar at St Pancras International, at Ebbsfleet International and at Ashford International due to speed restrictions resulting from poor weather conditions.
TRAVEL: Thousands of travellers faced disruption after Eurostar services were delayed by an overhead power cable fault in France. The first scheduled service to Paris ran as normal at 5.40am, but four later services have already been cancelled.Eurostar expects to run a normal service from lunchtime