Virgin has cancelled 20 trains because of the rocketing temperatures as a heatwave sweeps across the nation and commuters brace themselves for what is predicted to be a chaotic rush hour this evening.
The train operator announced it would be cancelling services running between London Kings Cross and Leeds due to the weather.
Today is now officially the hottest day ever recorded in July as temperatures passed 35C (95F).
Yesterday, some First Great Western fast train services had to be redirected to avoid vulnerable parts in the track and today's rush hour looks set to become far busier as services are forced to cancel due to the sweltering heat.
Virgin Trains East Coast said it would be cancelling 10 northbound and 10 southbound train services between London Kings Cross and Leeds today due to the heat..
The details of the 20 trains affected are listed on the train operator's website.
— Virgin Trains EC (@Virgin_TrainsEC) July 1, 2015
A Virgin Trains East Coast spokesman said: "Due to today's hot weather, and in the interest of safety, Network Rail has advised that sections of the East Coast Main Line between London and Retford are subject to temporary speed restrictions.
"As a result a limited number of mostly off-peak services between London and Leeds have had to be cancelled today. An hourly service is still in operation throughout the day between London and Leeds."
Virgin Trains said that those who have tickets for one of the cancelled trains can use them on the train before or after. Alternatively the operator will offer a refund.
Passengers say that the train cancellations are already causing carriages to become busy as commuters cram onto the services that are running.
First Great Western confirmed that it will be running a slower service today because of the heat, but are not expecting the same cancellations at Virgin Trains East Coast.
FGW said that Network Rail's speed restrictions will mean that direct London Paddington to Bourne End services will terminate at Maidenhead from 12pm to 8pm.
A train shuttle service will be in place to carry passengers between Maidenhead and Bourne End.
High Speed Train services are expected to run as normal, however there may be delays as services past through the affected area and some services may be cancelled to protect the evening peak.
East Midlands Trains said that trains might be travelling at reduced speeds but they are not expecting any cancellations.
EMT's website states: "Because of today's expected high temperatures we have been advised by Network Rail that safety speeds are likely to be introduced on some of our routes. This means that some of our trains may have to run at reduced speeds.
"We expect to still be able to run a full timetable but you may experience some minor delays."