Working in a Heatwave: What to Wear and How to Stay Safe on Site

UK summers are getting hotter. The 2022 heatwave broke 40°C for the first time on record, and HSE data consistently shows that heat-related illness is one of the most underreported risks in the construction and trades sector. Most workers know to drink water. Fewer think carefully about what they're wearing - or how their clothing choices affect how their body handles heat over a full working day.

This guide covers the practical side of working in hot weather: what to wear on a building site or in a tight space in high temperatures, how to protect yourself from heat stress, and what the warning signs look like. It applies whether you're laying blocks in direct sun, pulling cable in a roof void, or working under a vehicle in a workshop.

Your body regulates temperature through sweating and blood flow. In hot, humid conditions - or when you're doing physical work - those systems can be overwhelmed. Heat exhaustion and heatstroke are not the same thing, and the difference matters.

Heat exhaustion is the warning stage: heavy sweating, pale and clammy skin, nausea, dizziness, muscle cramps, and a fast, weak pulse. Move somewhere cool, drink water, and rest. Most people recover within 30 minutes.

Heatstroke is a medical emergency. The body has stopped cooling itself effectively. Skin becomes hot and dry or flushed, confusion and disorientation set in, and the person may lose consciousness. Call 999. Do not wait to see if they improve.

The people most at risk are those working outdoors in full sun, those in confined or enclosed spaces where heat builds up (roof voids, loft conversions, plant rooms), and those wearing heavy or non-breathable clothing. Understanding that last point is where workwear choices actually make a difference.

The honest answer is that full-length lightweight trousers are often the better choice in hot weather - not for comfort, but for protection. Direct sun on bare legs significantly increases UV exposure and dehydration risk, and on site there is always the question of skin contact with abrasive or hazardous materials.

That said, in conditions above 30°C, breathable work shorts are a practical alternative for trades where bare legs present no particular hazard - decorators, carpenters working indoors, electricians who aren't working in contaminated environments.

For trousers, the key is fabric weight and construction. Heavy canvas trousers that serve you well in autumn will be genuinely harmful in a heatwave. Look for:

• Stretch trousers - 4-way stretch fabrics move with you and typically use lighter synthetic blends that breathe better than canvas. The Snickers 6800 LiteWork is built specifically for warm conditions, using a lighter stretch fabric than the AllroundWork or FlexiWork lines. The Helly Hansen Chelsea Evolution stretch fabric performs similarly - it moves air as you move, rather than trapping it.
  
  

• Ripstop fabrics - Ripstop weaves are lighter than standard canvas and still durable. The Apache Ripstop trouser is a sensible option for painters, decorators, and light trades who need to keep costs down but want something more breathable than standard polycotton canvas.

For work shorts in hot weather, the full workwear shorts range covers everything from elasticated waist lightweight options to stretch cargo styles. Where hi-vis is required, the hi-vis shorts range gives you compliance without the heat penalty of full-length hi-vis trousers.

In direct sun, loose-fitting, light-coloured clothing that covers your arms reduces UV exposure and helps your body manage heat more effectively than a bare upper body - counter-intuitive but accurate, as the fabric shields you from radiant heat.

• Work t-shirts - A moisture-wicking work t-shirt is better than a cotton one in genuine heat. Moisture-wicking fabrics move sweat away from the skin and let it evaporate, which is how your body cools itself. A saturated cotton t-shirt loses that function and sits damp against you.
  
  

• Work polo shirts - The collar adds a small amount of neck protection. For trades where you're moving between sun and shade, a polo is a practical middle ground.
  
  

• Hi-vis tops and hi-vis vests - If your site requires hi-vis, a vest worn over a breathable t-shirt is significantly more comfortable in heat than a full hi-vis jacket. Where regulations allow a vest rather than a sleeved garment, use it. Where a sleeved garment is required - rail work under RIS 3279-TOM, for example - look for the lightest available option rather than defaulting to a winter-weight jacket.

A hard hat in full sun will significantly increase the heat felt at head level. Ventilated hard hats are available and worth the minor extra cost in summer. When a hard hat is not required, a wide-brim sun cap or workwear cap provides basic UV protection to the face and neck - an area that takes heavy cumulative sun exposure over a working life.

A full leather safety boot in 30°C heat is uncomfortable and generates significantly more foot heat than a breathable safety trainer. For any work that does not specifically require the ankle protection or waterproofing of a boot, switching to safety trainers in summer is a practical decision.

The composite toecap is worth noting here specifically: steel toecaps conduct heat. On a hot day, a steel toe in a boot sitting in the sun will hold and conduct that heat to your foot. Composite toecaps - fibreglass or carbon fibre - do not conduct heat or cold in the same way. If you're buying summer safety footwear, the non-steel composite toe range is worth considering for this reason alone, as well as the lighter overall weight.

Safety shoes are another option for trades where the full ankle support of a boot is not a requirement - warehouse work, indoor trades, or driving roles.

This is overlooked. A wool-blend or moisture-wicking work sock manages foot moisture significantly better than a standard cotton sock in hot conditions. Wet feet in a safety boot lead to blisters and discomfort that compounds over a long shift. It's a small thing with a meaningful effect on the end of a hot day. 

The combination of physical exertion, direct UV exposure, and hot ground surfaces makes this the highest-risk environment for heat illness. Lightweight stretch trousers over shorts, a moisture-wicking hi-vis top, composite safety trainers or lightweight S3 boots, and a ventilated hard hat covers the basics. Schedule the most physically demanding work for early morning where possible.

Roof voids, loft spaces, and floor voids can reach temperatures well above ambient air temperature on hot days. The problem here is not just ambient heat but radiated heat from surfaces that have been in the sun all morning. Confined space work should be time-limited on hot days - short rotations with recovery time outside rather than extended periods in the space. Lightweight stretch trousers perform better than canvas in these conditions. Bring water into the space; do not rely on drinking only at breaks.

Indoor environments are generally more manageable but can become very hot in loft conversions, conservatories, or rooms with significant south-facing glass. Ripstop or stretch lightweight trousers, a moisture-wicking t-shirt, and safety trainers rather than boots is a sensible standard setup.

Cab temperatures can exceed ambient by a significant margin even with air conditioning, particularly during starts and stops. Lightweight clothing, hydration kept in the cab, and regular breaks out of the vehicle are the main mitigations. Avoid heavy outerwear in a cab - it traps heat against your body even when you feel the aircon working. 

Aim for around 500ml to 1 litre of cool water per hour during hot, active work - sipped steadily throughout the shift rather than drunk in large quantities at once. Most workers fall well short of this because they wait until they feel thirsty. Thirst is a late indicator, not an early one.

Cold water is more effective than warm or room-temperature water. If you have access to refrigeration on site, use it for drinking water. Electrolyte tablets or drinks help on very hot days when significant sweating has been occurring for several hours - plain water replaces fluid but not the salt and minerals lost through sweat.

Avoid alcohol the evening before a day expected to be hot. Caffeine in moderate quantities is not dehydrating in the way it was once thought, but energy drinks in high heat are not a substitute for water.

SPF30 minimum on all exposed skin. Apply before work, not once you arrive. Reapply at lunchtime - sweat and physical activity reduce the effective protection over time. The back of the neck, the forearms, and the face are the highest-exposure areas for outdoor trades.

Sunburn is not just uncomfortable - it reduces your body's ability to regulate temperature effectively, making heat illness more likely for the rest of the day and into the following days.

If you are responsible for others on site, or working as part of a crew, know what to look for:

Heat exhaustion - heavy sweating, pale or clammy skin, fast weak pulse, nausea, dizziness, muscle cramps, headache, fainting. Move them to shade or a cool space, loosen clothing, give cold water to sip, apply cold wet cloths to skin. If they do not improve within 30 minutes, treat as heatstroke.

Heatstroke - hot dry or flushed skin (sweating has stopped), confusion, slurred speech, loss of consciousness, seizure. Call 999 immediately. Cool them down as fast as possible while waiting for emergency services - cold water on skin, fanning, ice if available.

Both conditions are preventable. Neither should be treated as a normal part of a hot day's work.

There is no specific maximum workplace temperature in UK law, but the Management of Health and Safety at Work Regulations 1999 require employers to assess and manage all risks to health - including thermal comfort and heat stress. The HSE recommends a risk assessment when temperatures regularly exceed 24°C in sedentary work or lower for physical work.

In practical terms: employers should provide access to cool drinking water, allow more frequent rest breaks during hot periods, make lighter work options available where possible, and not pressure workers to continue when they are showing signs of heat illness.

Lightweight stretch or ripstop work trousers, a moisture-wicking t-shirt or polo, a hi-vis vest if required, composite toe safety trainers rather than full leather boots, and a ventilated hard hat. Avoid heavy canvas trousers and leather jackets in high temperatures. 

In direct sun, yes - loose light-coloured long sleeves reduce UV exposure and actually help your body manage heat by shielding it from radiant heat. The key is the fabric being lightweight and breathable. Heavy materials in direct sun make things worse, not better. 

Aim for 500ml to 1 litre of cool water per hour during active work in hot conditions, sipped steadily throughout. Do not wait until you feel thirsty. Cold water is more effective than warm. 

Depends on your employer's site rules and the specific hazards. Many sites permit shorts during hot weather. Where contact with hazardous materials, abrasive surfaces, or significant UV exposure is a factor, lightweight full-length trousers are generally safer. Check site policy first. 

Breathable safety trainers or safety shoes rather than full leather boots where the work allows it. Composite toecaps are preferable to steel in hot weather as they do not conduct heat in the same way. Pair with a moisture-wicking work sock to manage foot sweat over a long shift. 

The workwear shorts range covers everything from lightweight cargo styles to stretch and elasticated options. For full-length lightweight trousers in hot weather, the Snickers trousers range and Helly Hansen work trousers are worth comparing for stretch and breathable options. Breathable tops are in the work t-shirts and polo shirts ranges. For summer footwear, the safety trainers and composite toe footwear collections are the best starting point.