With London and the South East due to experience possibly their hottest temperatures ever later today, disruption to train services is expected, as speed restrictions are in force to avoid rails buckling in the extreme heat.
Restrictions and alternative timetables are due to be implemented from lunchtime onward as temperatures peak — so just because you got into work OK this morning, don't assume you'll be fine on the way home. If you are struggling, might we suggest heading for your nearest beer garden or rooftop bar and sitting rush hour out?
Changes vary across different train operators, but here's what we know so far (this is likely to change throughout the afternoon/evening as the situation develops):
The tube and TfL services
Despite the stifling heat underground, no changes are anticipated on tube services — although we wouldn't be surprised to hear of a few delays due to people fainting on board tube carriages. Drink your water, people. This tube map showing which lines are air-conditioned is also a useful addition to your commuting toolbox.
Journeys across the Southeastern network are liable to changes from lunchtime, with Southeastern advising against travel where possible. Online journey planners (NOT timetables) on the Southeastern website have apparently been updated with the changes, so type in your usual journey to see whether it's expected to run as normal. It's worth keeping an eye on the Southeastern Twitter feed for the latest updates.
Southern is warning of changes from 10am and, again, advises against non-essential travel. As with Southeastern, the journey planners on the Southern website should now be updated with today's changes, so check before you head to the station. For up-to-date news, check Southern's Twitter feed here.
South Western Railway
At time of writing, South Western Railway hasn't announced specific changes, although it does offer some advice for travelling in hot weather. That said, Waterloo station — South Western's main London terminus — is notorious for disruption wrought by heat-damaged rails, so we wouldn't be surprised to see something going awry. Keep an eye on the website, main Twitter and customer services Twitter.
Great Western Railway
Speed restrictions are in place from 12pm-8pm between Paddington, Didcot Parkway and Banbury. With these trains taking longer to reach their destinations, later delays are a possibility. And trains between London and South Wales are only running hourly instead of half-hourly. Check the Great Western Railway website and journey planner, and follow on Twitter for updates.
Chiltern is warning of minor delays between 12pm and 8pm due to those speed restrictions, with no trains stopping at Little Kimble or Monks Risborough during this period. Check the website and Twitter for latest updates.
Virgin Trains West Coast
London Northwestern Railway
The main routes affected on London Northwestern Railway are between Euston and Rugby, and Watford Junction and St Albans, according to Twitter. Stay up to date there, or check your journey on the London Northwestern Railway website.
LNER passengers are warned against travelling unless essential. Speed restrictions are in place between King's Cross and Peterborough, with delays of up to 35 minutes likely. Elsewhere on the LNER network, there's a reduced timetable, and if you had a ticket for today but decide not to travel (wise move), it'll be valid Friday, Saturday or Sunday instead. Updates on the LNER website and Twitter.
Greater Anglia is another operator advising customers against travel unless absolutely necessary (the headline 'Do not travel' on its website is particularly ominous). Specific details for which services are affected are scarce, with the company saying 'our usual timetable is unable to operate'. Check your journey before you travel, and as always, Twitter is your friend.
All operators are expecting a normal service to resume on Friday, but do check before you travel, as disruption on Thursday may leave train carriages displaced, with a knock-on effect into Friday rush hour.