Alex is Sprintlaw’s co-founder and principal lawyer. Alex previously worked at a top-tier firm as a lawyer specialising in technology and media contracts, and founded a digital agency which he sold in 2015.
When the UK gets a heatwave, it doesn’t just make customers grumpy and stock rooms uncomfortable - it can create real health and safety risks for your business.
A question we hear a lot from small business owners is: what temperature is too hot to work?
The tricky part is that UK law doesn’t give a simple “stop work at X°C” rule. Instead, your legal duties focus on keeping the workplace at a reasonable temperature and controlling the risks of heat exposure.
In this guide, we’ll walk you through what the law expects, how to make practical decisions during hot weather, and how to protect your business (and your team) from day one.
Is There A Legal Maximum Temperature At Work In The UK?
In short: no, there isn’t a single legal “maximum temperature” that applies to all workplaces in the UK.
That’s why people searching what temperature is too hot to work (or “how hot is too hot to work”) can find it frustrating - the answer depends on the circumstances.
Instead of setting a maximum, UK rules generally require you to ensure that the temperature in indoor workplaces is reasonable and that you manage health and safety risks.
What The Law Actually Says (In Plain English)
Employers in the UK have broad duties under health and safety law to protect workers from harm. Heat-related illness (like heat exhaustion or heatstroke) is a foreseeable risk in hot conditions - so it’s something you’re expected to plan for.
This is not just about comfort. If people are getting dizzy, dehydrated, fainting, or making mistakes because the workplace is too hot, you’re looking at a safety risk (and potentially a legal risk) as well.
What About Minimum Temperature Rules?
While there’s no set maximum, there is guidance around minimum indoor temperatures. You may have heard the commonly quoted thresholds:
- 16°C for most indoor work
- 13°C where the work is physically demanding
It’s worth being clear that these figures are typically cited as HSE guidance on what’s likely to be “reasonable” in cold conditions - they’re not a universal legal cut-off that applies to every workplace in every situation. For heat, the approach flips: you still look at what is “reasonable” in context - and you take steps to reduce risk where the workplace is getting excessively hot.
So What Temperature Is Too Hot To Work?
Because there’s no single legal maximum, the best way to answer what temperature is too hot to work is to treat it as a risk assessment question.
The “too hot” point will vary depending on factors like:
- Humidity (heat + humidity can be significantly more dangerous)
- Air movement/ventilation (stagnant air makes heat stress worse)
- Work type (heavy manual work generates body heat)
- Workplace layout (kitchens, warehouses, loft offices, shopfronts with direct sun)
- Clothing/PPE requirements (can reduce heat loss)
- Worker vulnerability (pregnancy, certain medical conditions, disability, medications)
- Duration of exposure (short bursts vs hours on end)
A Practical Way To Think About “Too Hot”
Rather than chasing a magic number, ask:
- Are people showing signs of heat stress (headaches, nausea, confusion, excessive sweating, faintness)?
- Is the heat causing a higher chance of accidents (slips, errors, reduced concentration, fatigue)?
- Are you able to keep conditions “reasonable” with practical controls (ventilation, breaks, water, scheduling changes)?
If the answer is “no”, you should treat it as a trigger to change how work is done, or in extreme cases, stop particular activities until conditions are safe.
Different Workplaces, Different Risk Levels
Two businesses can experience the same outdoor temperature and have very different workplace risk profiles.
- Offices: often more controllable (shading, fans, air con, flexible dress code, remote work options).
- Retail and hospitality: customer-facing requirements, heat from lighting/equipment, busy peak periods.
- Kitchens: consistently high ambient heat, hot surfaces, limited cooling options.
- Warehouses and workshops: large spaces that trap heat, heavy lifting, sometimes limited airflow.
- Construction/outdoor work: direct sun exposure, dehydration risk, PPE, and higher physical strain.
This is why it’s safer (and more defensible) to rely on a documented risk assessment and sensible controls, rather than a blanket “we shut at 30°C” policy that might not fit your reality.
Your Employer Duties During Hot Weather (What You Need To Do)
When temperatures rise, your legal obligations as an employer don’t disappear - if anything, your health and safety duties come into sharper focus.
As a small business owner, the goal isn’t to create perfect comfort at all times. It’s to show you’ve taken reasonable steps to keep people safe.
That includes practical measures and clear communication, backed by proper documentation (especially if you ever need to justify decisions later).
1) Carry Out (And Update) A Heat Risk Assessment
If hot conditions could create harm, you should assess the risks and record sensible control measures. This is especially important where you have:
- manual handling or physically demanding work
- hot machinery or enclosed spaces
- workers wearing PPE
- workers who may be more vulnerable to heat
A risk assessment doesn’t have to be complicated - but it should be real, site-specific, and reviewed when conditions change (like a sudden heatwave).
2) Keep Workplace Temperature “Reasonable”
In indoor workplaces, regulations expect you to ensure a reasonable temperature.
What counts as “reasonable” is fact-dependent - but common controls include:
- providing fans and improving airflow
- using blinds or reflective film on sunny windows
- adjusting workstation location away from direct sun/heat sources
- reviewing dress code requirements (where safe and appropriate)
- reducing heat generated by equipment where possible
For broader planning around staff welfare and safety standards, it can help to capture your expectations in a clear Workplace Policy that covers things like safety, conduct, and operational changes in unusual conditions.
3) Provide Drinking Water, Rest Breaks, And Safe Working Practices
When it’s hot, dehydration becomes a safety issue quickly - especially for physically active roles.
In practice, you should consider:
- easy access to cool drinking water
- reminding staff to hydrate (don’t assume people will)
- additional rest breaks and shaded/cooler break areas
- job rotation to reduce continuous heat exposure
Heat is also a good time to double-check that your break arrangements are lawful and workable in real life. The rules on rest and lunch breaks can be the baseline, but in hot conditions you may need to go further to keep things safe.
4) Consider Working Time And Scheduling Changes
Sometimes the best heat control is operational - not physical.
Common options include:
- starting earlier and finishing earlier (to avoid peak heat)
- reducing strenuous tasks during the hottest hours
- increasing staffing levels to reduce individual workload
- allowing remote work (where the role allows)
Be careful if heat leads you to change hours frequently. Working time limits and record-keeping still matter, including under the Working Time Regulations and rules around the maximum daily working hours.
If you want flexibility, it’s worth making sure your staffing documents are drafted properly so you’re not “making it up as you go” each summer.
5) Communicate Clearly With Your Staff
Heat-related problems often escalate because staff don’t know what they’re allowed to do - for example, whether they can take extra water breaks, swap tasks, or report feeling unwell without getting into trouble.
Set expectations early, such as:
- who to report heat concerns to
- what signs of heat exhaustion to watch for
- when extra breaks are available
- what adjustments you’ve approved (dress code, scheduling, task changes)
From a legal protection point of view, it helps if these expectations are reflected in your Employment Contract and supported by a consistent handbook approach (particularly as your team grows).
Special Scenarios: Vulnerable Workers, PPE, And Customer-Facing Teams
Heat doesn’t affect everyone equally - and one of the most common mistakes small businesses make is treating heat management as “one rule for everyone”.
In reality, you may need different controls for different roles and individuals.
Workers With Additional Health Risks
You should take extra care where a worker is more vulnerable to heat - for example:
- pregnant workers
- older workers
- workers with certain medical conditions or taking certain medications
- workers with disabilities (where heat sensitivity may be relevant)
This isn’t about asking intrusive questions. It’s about creating a culture where staff can raise concerns and you consider reasonable adjustments where appropriate.
If you handle health information as part of managing workplace safety, remember that medical data is sensitive personal data. Make sure your data handling practices are properly thought through under your Privacy Policy and internal HR processes.
PPE And Uniform Requirements
If PPE is required for safety, you generally can’t relax it just because it’s uncomfortable - but you may need to introduce other controls to reduce heat stress, such as:
- more frequent breaks
- cooler break spaces
- lighter PPE alternatives (where they still provide adequate protection)
- job rotation
If uniforms are about branding rather than safety, you’ll often have more flexibility. For example, allowing breathable fabrics, lighter colours, or more relaxed options during hot spells can be a simple win.
Customer-Facing Workplaces
In retail, hospitality, gyms, and clinics, there’s an extra factor: your customers are in the space too.
If your workplace is uncomfortably hot, you’re not only risking staff wellbeing - you may also face:
- higher customer complaints and reputational risk
- refund disputes (if services are materially impacted)
- staff shortages (if people go home unwell)
That’s why it’s worth treating heat planning as part of your operational risk management, not just a “nice-to-have”.
Can Employees Refuse To Work If It’s Too Hot?
This is where many small business owners feel stuck - you want to do the right thing, but you also need the business to keep running.
In general terms, if an employee reasonably believes there’s a serious and imminent danger, they may be protected if they leave the workplace or refuse to return. In practice, these protections can arise under the Employment Rights Act 1996 (including sections 44 and 100) where the employee takes (or proposes to take) appropriate steps to protect themselves or others.
That doesn’t mean staff can automatically walk out because it’s warm. But it does mean you should take heat complaints seriously, investigate quickly, and document the steps you take.
How To Handle A “It’s Too Hot” Complaint (Without Escalating It)
If a team member says the workplace is too hot to work, a sensible approach is:
- Acknowledge the concern and ask what symptoms or risks they’re experiencing (if any).
- Check the conditions (temperature, ventilation, humidity, workload intensity, PPE).
- Apply controls immediately where possible (water, breaks, fans, task changes, moving workstations).
- Record what you did (even short notes can help later).
- Escalate if the risk remains (adjust hours, reduce tasks, close an area, or stop work).
These situations are much easier to manage when your expectations are already set out clearly in writing - for example, in a staff handbook that explains workplace safety, reporting lines, and operational changes during extreme weather. As your business grows, a Staff Handbook can help you apply consistent rules across your team.
Be Careful With Disciplinary Action
If you jump straight to disciplinary action when someone raises a heat safety concern, you risk escalating a manageable situation into a formal dispute.
Even if you suspect someone is being difficult, it’s usually better to:
- assess the safety issue first
- apply reasonable controls
- then address performance/conduct separately (if needed)
Handled calmly, most heat concerns can be resolved quickly with common-sense adjustments.
Heatwave Checklist For Small Business Employers
If you want a quick, practical way to prepare for the next hot spell, here’s a simple checklist you can actually use.
Workplace Setup
- Check airflow and ventilation (can you improve it today?)
- Set up fans or portable cooling where appropriate
- Use blinds/shading on windows with direct sun
- Move workstations away from sun-facing glass where possible
- Identify the hottest zones (kitchens, stock rooms, upstairs offices)
Work Organisation
- Adjust shifts to avoid the hottest hours (where you can)
- Reduce strenuous tasks at peak heat times
- Rotate tasks so no one is stuck in the hottest role for hours
- Plan extra breaks and ensure they’re covered operationally
People And Policies
- Remind staff of heat stress symptoms and reporting lines
- Make water easily accessible and encourage hydration
- Review uniform expectations (safety vs branding)
- Consider reasonable adjustments for vulnerable workers
- Document what you decided and why (risk assessment notes)
Legal Foundations
- Make sure your approach aligns with your core health and safety duties
- Check working time limits if you’re changing hours frequently
- Keep your HR documents up to date so expectations are clear and consistent
Done well, this doesn’t just help you survive heatwaves - it helps you run a safer, more resilient business year-round.
Key Takeaways
- There isn’t a single legal maximum temperature in the UK, so what temperature is too hot to work depends on the workplace and the risks involved.
- Your legal focus should be on keeping workplace temperature reasonable and controlling the risk of heat-related illness and accidents.
- A heat risk assessment (kept practical and up to date) is one of the best ways to make defensible decisions during hot weather.
- Simple controls like ventilation, fans, water access, extra breaks, and scheduling changes can significantly reduce risk.
- You may need extra steps for vulnerable workers, PPE-heavy roles, and high-heat environments like kitchens and warehouses.
- Clear written policies and employment documents help you apply consistent rules and reduce the risk of disputes when temperatures spike.
If you’d like help reviewing your workplace policies or employment documents so you’re legally protected in extreme weather (and everyday operations), you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.
