Temperatures are forecast to hit the mid-30s on Monday (June 30) and Tuesday (July 1), potentially marking the hottest days of 2025 so far.
As a result, between 10am and 7pm on both days, there will be an emergency speed restriction between East Croydon and Burgess Hill due to predicted high temperature.
Trains may be cancelled, delayed by up to 10 minutes, or revised during that period.
Journeys to or from Brighton and the coastal areas which travel via Burgess Hill and East Croydon may see journey times increased by up to 10 minutes.
Trains will be busier than usual, in particular on routes to the coast throughout the day.
Gatwick Express services will run between London Victoria and Gatwick Airport only.
Southern services that run from London Victoria and Littlehampton via Hove will now terminate at West Worthing and then restart from Worthing back to London Victoria.
As there will be a reduced service between Littlehampton and Brighton, please make sure you plan your journey prior to leaving.
London is currently under an amber health warning after it was issued by the UK Health Security Agency, and it will be in place until Tuesday (July 1).
Passengers travelling through Croydon are urged to check before they travel, allow extra time, and carry water to stay hydrated.
With delays and cancellations expected at East Croydon during the hottest spell of the year so far, planning ahead is essential to avoid disruption.
