When the Thermometer Climbs: Seasonal Fire Hazards Every UK Facilities Manager Should Watch

The United Kingdom is not a country traditionally associated with extreme heat. Yet in recent years, the Met Office has issued amber warnings with increasing regularity, and the summer of 2022 — when the mercury breached 40°C for the first time on record — served as a stark reminder that our building stock was largely never designed for such conditions.

For facilities managers, a heatwave is not merely an exercise in keeping staff comfortable. Sustained high temperatures alter the fire risk landscape of a commercial premises in ways that many standard assessments, conducted in cooler months, fail to fully anticipate.

Electrical Systems Under Sustained Strain

Electrical faults remain one of the leading causes of workplace fires in the UK, and heat compounds the problem considerably. Cables, distribution boards and portable appliances are typically rated for ambient temperatures well below those recorded during recent summers. When a server room or plant room already runs warm, an additional ten degrees of ambient heat pushes insulation materials closer to their thermal limits.

Overloaded circuits are a particular concern. The summer surge in air conditioning units, portable coolers and fans — often plugged into circuits never intended to carry such loads — creates a predictable recipe for overheating. We have attended premises where a single daisy-chained extension lead feeding three desk fans was the ignition source for a serious incident.

A thermal imaging survey of distribution boards before peak summer is a prudent investment. It identifies hot spots long before they become emergencies.

The Lithium-Ion Question

Few hazards have grown as quickly in the past decade as lithium-ion battery failure. E-bikes, e-scooters, power tools, laptops and backup power supplies all pack significant energy density into compact cells. When these batteries are charged in direct sunlight, stored in warm storerooms or left charging unattended overnight in a hot building, the risk of thermal runaway rises sharply.

A battery experiencing thermal runaway can reach several hundred degrees Celsius within seconds and produce toxic flammable gases. Standard extinguishers are frequently ineffective against a established lithium-ion fire.

Practical steps include designating cool, well-ventilated charging areas away from escape routes, prohibiting overnight charging of personal e-mobility devices on site, and ensuring staff understand the warning signs — swelling, hissing, unusual heat or a sweet chemical odour.

Dried Vegetation and the Perimeter Problem

Extended dry spells turn grass verges, embankments and landscaped grounds into ready fuel. A discarded cigarette at a rear smoking shelter, a spark from grinding work or even focused sunlight through a glass bottle can ignite dry vegetation, and fire can travel rapidly toward a building's exterior, compromising fire doors, loading bays and external storage.

Facilities managers should keep vegetation around the perimeter cut short during summer months, maintain clear zones beneath external cladding and canopy structures, and ensure waste and recycling storage does not sit against the building envelope. Bonfires and hot works on site should be subject to stricter permit controls during dry periods.

Sprinklers, Extinguishers and Equipment Readiness

Heat does not only create ignition sources; it can degrade suppression and detection equipment too. Extinguisher pressure gauges should be checked more frequently in summer, as temperature fluctuations can affect readings. Sprinkler systems, fire alarms and smoke control systems all deserve a warm-weather service check to confirm they will perform when needed.

Equally important: ensure escape routes remain unobstructed by seasonal clutter. Summer often brings stock overflow, event equipment and open windows propped with makeshift wedges — all of which can compromise compartmentation and escape provisions.

A Heatwave-Ready Seasonal Checklist

Before the next amber warning is issued, we recommend facilities managers work through the following:

• Commission a thermal imaging survey of electrical distribution equipment
• Review circuit loading, particularly where cooling appliances have been added
• Establish a policy for lithium-ion battery charging and storage
• Keep perimeter vegetation trimmed and remove combustible waste from building exteriors
• Verify extinguisher gauges and service records are current
• Confirm fire doors, dampers and compartmentation have not been compromised
• Brief staff on summer-specific hazards, including smoking area discipline
• Review the fire risk assessment to ensure it reflects seasonal conditions

Compliance That Moves With the Seasons

The Regulatory Reform (Fire Safety) Order 2005 requires fire risk assessments to be kept under review — and a review that ignores seasonal variation is only half a review. At Mercury Fire Safety, our assessors build seasonal risk factors into every assessment, ensuring your documentation reflects the conditions your premises actually face throughout the year.

Heatwaves will continue to test UK buildings. With preparation, they need not test your fire safety compliance.