Slough, home to a campus owned by Equinix and Digital Realty and hosting computing for Amazon, Google, Oracle, and Microsoft, ran several degrees hotter than its surroundings during Europe's record June heatwave, and Cambridge researchers warn the data center heat island effect…
When the heat dome settled over southern England last week, weather stations near a data-center campus on the edge of Slough recorded temperatures running several degrees higher than the surrounding area, according to The Guardian's original reporting. One local resident described the heat as feeling like "pinching your body and burning your skin," a sensory detail that captures something the planning files do not. The pattern matches what meteorologists call a heat island, and it points to a problem that climate researchers at the University of Cambridge have begun to quantify, and that European planning regimes were never built to handle.
Slough, a town roughly 25 miles west of central London near Heathrow, hosts what The Guardian describes as the continent's largest data-center campus. The site is owned and maintained by Equinix and Digital Realty and provides computing power for Amazon, Google, Oracle, Microsoft, and others, drawing enormous amounts of electricity to run servers and even more to cool them. The cooling equipment dumps heat into the surrounding air. During a record-breaking June heatwave that pushed thermometers toward 100°F across parts of southern England, that exhaust piled on top of an already brutal climate, producing what meteorologists call a heat island: a developed area running noticeably hotter than the countryside around it.
The local temperature difference is now small enough to measure. According to The Guardian, weather station data showed temperatures near the facility reaching 36.7°C and 36.5°C at the nearest station (ISLOUG2), compared to 36.2°C and 34.7°C at the town-centre station — a measurable delta in an already extreme heat event. A recent analysis from researchers at the University of Cambridge, not yet peer-reviewed and available on arXiv, suggests that data centers could eventually expose up to 340 million people across Europe to additional heat-stress risk by mid-century if the current build-out continues without mitigation. That number is a forward-looking projection, not an observed impact, and it depends on assumptions about how aggressively the industry grows, how efficiently it cools, and how hot Europe gets. The direction, however, is consistent with what residents near Slough are already feeling.
Local complaints about the campus have been accumulating for years. Residents including Nabeel Nawaz, Didier Kindembe, and Naveed Hussein have cited surging electricity prices they blame partly on industrial demand, water-pressure drops tied to cooling loads, and a constant low-frequency hum that drifts across nearby housing. None of those grievances is new to data-center siting disputes. In the United States, the politics of that backlash have already started reshaping elections. What is new in Slough is that the heat itself has now become visible in the temperature record. The campus is effectively a small power plant in reverse. It does not burn fuel to make electricity, but it consumes electricity to move heat from inside its buildings into the air outside them. During a heatwave, that exhaust becomes the climate of someone's back garden.
UK and EU policymakers have so far treated data centers as a grid and water problem: how much electricity they will demand, how much water they will drink, and whether renewable-power contracts can keep pace. The heat they push out has not been on the planning checklist. There have been proposals to capture data-center waste heat and pipe it into district heating systems, a sensible idea that, in countries with cold winters and old housing stock, would offset a meaningful share of residential fossil-fuel use. The Slough cluster sits near dense housing, but it is not currently wired to any district network.
That gap is the story. The AI buildout is the fastest-growing slice of European electricity and water demand, and it is now producing a measurable local heat externality that no existing planning regime is equipped to price, restrict, or redirect. Each new campus sited in a heat-exposed region will inherit the same trade-off: cheap land and cheap power traded against warmer summers for the people who already live there. The question is no longer whether data centers affect their neighbors. It is whether regulators will treat their heat output like other industrial emissions, or whether every town that hosts one will discover the externality the way Slough just did, through the skin.