Rail passengers in the east are being urged to avoid unnecessary travel as efforts continue to repair damage to the network caused by the record-breaking temperatures yesterday.
Network Rail is urging commuters planning to use the Midland Main Line between St Pancras and Sheffield, which serves Luton, Bedford and Kettering to check before travelling due to reduced service levels.
Meanwhile, Great Northern, Thameslink, East Midland Trains and West Midlands Trains warned of fewer carriages on some services, cancellations and continuing disruption.
Yesterday saw significant disruption on the rail route which links Sheffield to London St Pancras International via the East Midlands and Bedfordshire. Trains had to run at reduced speeds, which also meant a reduced service ran and those which did run were extremely busy."
Train speeds are being reduced to cut the likelihood of steel tracks buckling after multiple incidents on the network, including problems with overhead equipment
Passengers are strongly advised to consider alternative travel arrangements and only travel if their journey is absolutely necessary. If passengers must travel, they are urged to check before travelling with their train operator or with National Rail Enquiries. Passengers should allow additional time for their journey and take plenty of water with them."
The weather is also causing difficulties to flights.
Numerous travellers at Stansted also reported delays and cancellations, with the airport telling one passenger on social media that air traffic control restrictions over the south-east of England prompted the problems.
The Met Office said a new record temperature for the month was set at 38.1C (100.6F) in Cambridge on Thursday afternoon, beating the previous record of 36.7C (98.1F) set at Heathrow in 2015.