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.