There is a cupboard at the back of almost every office in the country. It has a laminate door that doesn't quite close properly, a faint smell of warm plastic, and a sign on it that says something like "COMMS — DO NOT BLOCK." Nobody blocks it, but nobody opens it either. Inside: a router, a network switch, a length of Cat5 that predates the coalition government, and possibly one of those small tower servers that was described as "temporary" at some point during the Obama administration. Nobody's been in since the Tuesday the broadband went down and Gary from accounts had a look, declared it "fine," and closed the door again. That was three summers ago. The cupboard has been doing its quiet, thankless work ever since — and this week, for the first time in a while, it is being asked to do that work in what is effectively a moderately enthusiastic oven.
The thing about British buildings is that they were designed around the assumption that warmth is a problem to be manufactured, not managed. Insulation goes in; ventilation is an afterthought; and the small internal room you've repurposed as a comms cupboard — with its one high window painted shut in 1987 — has the thermal properties of a Tupperware box left on a car dashboard. Your kit in there is already generating heat of its own. Add an ambient temperature that has, outside, been doing things not seen in living memory, and you have a situation.
The next few days represent a quietly serious test of whether your business can keep the lights on. Our position at Finnwood is straightforward: check the temperature in that cupboard today. A £40 thermometer and a spare fan are cheaper than an afternoon of downtime, and substantially cheaper than what comes after that.
Here are the numbers that make this more than a general anxiety. A third heatwave began on 4 July, with temperatures peaking at 35.5°C in Wisley, Surrey — marking the eighth day of the year when temperatures exceeded 34°C, breaking the country's record for the highest number of days exceeding this threshold in a single year. It is also the first year in the UK weather record to see temperatures reach 35°C or higher in May, June and July. That is not a background statistic. That is the context in which the building your kit lives in has been sitting, day after day, absorbing heat it was never designed to shed. Server room temperatures above 35°C can cause immediate operational problems, leading to system failures, outages, and potential data loss. The outside air this week has been comfortably close to that figure. Inside a sealed, unventilated cupboard, with a switch and a router generating their own warmth on top of it, you are in a different conversation altogether.
The illustration that everyone in IT has been talking about this fortnight is Cambridge's Dawn supercomputer. The heatwave that struck the UK late last month resulted in the University of Cambridge's Dawn supercomputer being knocked offline, with the outage occurring on 27 June due to excessive temperatures. It's believed the incident was caused by a failure with the cooling system at the West Cambridge data centre, where Dawn is housed. Dawn is one of the fastest AI supercomputers in the UK. It has a £36 million government investment behind it. It has a dedicated cooling infrastructure. And it still went down. Scientists previously warned that extreme weather exacerbated by climate change — including more intense heatwaves — posed a risk to supercomputers. If the warning applied there, it applies with considerably more force to the Netgear switch balanced on top of a cardboard box of old invoices in your back office. The same week Dawn went down, Queen Alexandra Hospital in Portsmouth declared a critical incident, with the NHS facility stating that chillers had failed at its on-site data centre, impacting digital services. These are not freak events. They are previews.
We have a longer case study if you want the full horror: an outage at two London hospitals during the 2022 heatwave cost £1.4 million, when two data centres supporting Guy's & St Thomas' NHS Foundation Trust collapsed amid record temperatures. Staff were forced to turn to paper, while appointments were cancelled or delayed — there were more than 100 delays, and one patient was unable to receive an organ transplant, causing "moderate harm." It took six weeks for services to fully return. And the kicker, the detail that should be printed on a laminated card and taped to the inside of every comms cupboard door in the country: the NHS review determined that the data centre outages were both preventable, and could have been avoided had the data centres been adequately prepared for managing cooling systems in the record-setting heatwave. Preventable. Not exotic bad luck. Not an act of God. A broken hose connector and a staff member who couldn't find the water supply in a hurry. That is the level of mundane tragedy we are discussing.
Now: your operation is not Guy's & St Thomas'. You do not have 371 legacy clinical systems and a contract with Atos. But the physics are identical. If the temperature of the server room becomes too high, the servers will overheat — and heat damage causes machine malfunction that can lead to permanent loss of data and server breakdown. A single overheated switch takes down your broadband. Your broadband going down takes down your phones, if they run over the internet — and they almost certainly do. Your phones going down means your card payments are next, and your access to any cloud system you depend on. The cascade happens fast and the recovery is slow, and none of it appears on any disaster plan, because nobody wrote one for "it got a bit warm in the cupboard next to the photocopier."
The practical steps are not complicated. Get a thermometer in there — for most enterprise server rooms, the practical takeaway is simple: keep your ambient temperature at or below 25°C. If you are above that, you want airflow. A decent tower fan pointed at the equipment will do a job in the short term. Make sure the cupboard door can actually circulate air — propping it open is inelegant but effective. If you have a proper server or network rack in there with no active cooling at all, call someone today rather than Wednesday, because Wednesday, with isolated locations potentially reaching 35°C, may be the day it becomes urgent in the expensive sense of the word.
The cupboard at the back of the office that nobody opens — that is the one that will decide your Tuesday. Gary from accounts had a look three summers ago and declared it fine, and to be fair to Gary, it was fine then: it was October. It is not October. If you would like someone who isn't Gary to have a proper look — check the temperatures, assess the airflow, and tell you honestly whether what's in there will still be speaking to you by Thursday afternoon — that is precisely the sort of thing Finnwood does. Give us a ring. We will bring a thermometer, and unlike Gary, we will not close the door again until we are sure.
