What Temperature Should a Hot Tub Be? Safe Settings Explained
What Temperature Should a Hot Tub Be? Safe Settings Explained
Quick answer: For most healthy adults, a hot tub should be set between 37°C and 38°C. Some people prefer up to 40°C, particularly in winter, but the water should never exceed 40°C. A cooler setting of 35°C to 37°C is usually more comfortable in summer.
Finding the best hot tub temperature is partly a matter of personal preference, but there are clear safety limits. The right setting should feel comfortably warm without making you feel dizzy, dehydrated or overheated.
This guide explains the recommended hot tub temperature for adults, children and different seasons, as well as how long to soak and what to do when the hot tub is not being used.
What Is the Ideal Hot Tub Temperature?
The ideal hot tub temperature for most adults is 37°C to 38°C. This is close to normal body temperature, so the water feels warm and relaxing without being as intense as the highest setting.
There is no single temperature that suits everyone. Use this simple guide as a starting point:
| Hot tub temperature | Best suited to |
|---|---|
| 35°C to 36°C | Hot weather, heat-sensitive users and a cooler soak |
| 37°C to 38°C | Comfortable everyday use for most healthy adults |
| 39°C to 40°C | Shorter, hotter soaks, often preferred in cold weather |
| Above 40°C | Not recommended |
If you are unsure where to begin, set the water to 37°C, allow it to reach the selected temperature and test how it feels. Adjust it by one degree at a time rather than immediately choosing the maximum.
What Is the Maximum Safe Hot Tub Temperature?
The maximum safe hot tub temperature is 40°C (104°F). The British and Irish Spa and Hot Tub Association advises that bathing in water above this temperature can be harmful, and 40°C is also the maximum stated in the European standard for domestic spas and hot tubs.
At higher water temperatures, the body has more difficulty releasing heat. This can increase the risk of overheating, dehydration, dizziness and fainting. The risk may be greater for children, pregnant people, older adults and anyone with an existing health condition.
A setting of 40°C is therefore a limit, not the temperature everyone should aim for. Many owners find 37°C or 38°C more comfortable for regular use. For further industry guidance, see WhatSpa’s explanation of the recommended hot tub temperature.
How Long Can You Stay in a Hot Tub?
For a healthy adult, a sensible session is generally around 15 to 30 minutes, depending on the water temperature, the weather and how you feel.
- At 39°C to 40°C, keep sessions shorter. Around 15 minutes is a cautious limit.
- At 37°C to 38°C, many adults may be comfortable for 15 to 30 minutes.
- At lower summer settings, you may feel comfortable for longer, but you should still take regular breaks.
Leave the hot tub immediately if you feel light-headed, unusually tired, nauseous, breathless or excessively hot. Drink water before and after your soak, and avoid using a hot tub after drinking alcohol or taking recreational drugs.
These timings are general guidance rather than a guarantee of safety. Your age, health, medication and sensitivity to heat can all affect how your body responds.
What Temperature Should a Hot Tub Be in Summer?
In summer, try setting your hot tub between 35°C and 37°C. On especially warm days, a temperature below body temperature can feel more refreshing and reduce the chance of becoming uncomfortably hot.
Some hot tubs can be set lower, although the minimum setting varies by model. If the water is already warmer than your chosen setting, changing the control panel will stop further heating but will not cool the water instantly.
To help a hot tub cool down:
- Lower the set temperature in advance.
- Remove the cover for a short period while the hot tub is supervised.
- Run the jets or air blower, if the manufacturer permits this.
- Replace a small amount of water with fresh, cooler water if needed, while keeping the water chemistry balanced.
Never add ice unless the hot tub manufacturer specifically allows it. Rapid temperature changes could affect the system, and untreated ice may introduce contaminants. South West Spas also offers a useful perspective on choosing an ideal hot tub temperature.
What Temperature Should a Hot Tub Be in Winter?
A winter hot tub temperature of 37°C to 40°C is comfortable for most adults. Many people choose 38°C or 39°C because the warm water contrasts pleasantly with the cold air without requiring the highest possible setting.
Do not increase the water above 40°C to compensate for cold weather. Instead:
- Keep the insulated cover fitted when the hot tub is not in use.
- Check that the cover seals properly and is in good condition.
- Follow the manufacturer’s frost-protection instructions.
- Keep the water circulating and heated unless the hot tub has been correctly winterised.
A well-insulated hot tub should maintain a steady temperature more efficiently than one that repeatedly cools and reheats.
What Temperature Should a Hot Tub Be for Children?
BISHTA advises a temperature nearer 36°C for children under 12, with continuous adult supervision. It also reports medical advice that children under four should not use a hot tub.
Children can overheat more quickly than adults, so sessions should be short and active supervision is essential. Make sure a child can stand with their head and shoulders comfortably above the water, and never treat a fitted cover, steps or rules as a substitute for supervision.
If you are uncertain whether hot tub use is suitable for a child, ask a healthcare professional first.
Can You Use a Hot Tub When Pregnant?
Pregnancy changes how the body handles heat and can increase the likelihood of overheating, dehydration and fainting. NHS-linked guidance notes that some people may choose to avoid hot tubs during pregnancy because research is limited and these risks remain.
If you are pregnant, speak to your midwife, GP or another qualified healthcare professional before using a hot tub. Follow their advice rather than relying on a general temperature or time limit, particularly during the first trimester.
Who Should Get Medical Advice Before Using a Hot Tub?
Ask a healthcare professional before using a hot tub if you:
- Are pregnant
- Have a heart or circulatory condition
- Have low or high blood pressure
- Take medication that affects blood pressure, alertness or heat regulation
- Have diabetes or another condition that affects temperature sensitivity
- Are recovering from illness or surgery
Do not use a hot tub if you feel unwell, have diarrhoea or have an open wound that cannot be fully covered with a waterproof dressing.
What Temperature Should You Leave a Hot Tub at When Not in Use?
If you use your hot tub regularly, it is often better to maintain a steady temperature or lower it slightly between sessions rather than turn it off after every use. How much energy this saves depends on the hot tub’s insulation, volume, heater, cover, outside temperature and electricity tariff.
For a short break from use, lower the temperature by a few degrees and keep the cover securely fitted. For a longer absence, follow the manufacturer’s away mode, economy mode or winterisation instructions. Do not simply switch the system off during freezing weather while it still contains water, as frozen water can damage pipes and components.
How Long Does a Hot Tub Take to Heat Up?
Many hot tubs warm by approximately 1°C to 2°C per hour, but heating time varies considerably. The starting water temperature, water capacity, heater output, insulation, cover quality and outdoor conditions all make a difference.
As a simple example, water starting at 15°C may take roughly 11 to 23 hours to reach 38°C at that heating rate. Treat this as an estimate and check the specification and instructions for your particular model.
Keeping the cover closed while heating reduces heat loss. If your hot tub offers scheduling or app controls, you may also be able to prepare it before you plan to use it.
How Can You Check the Water Temperature Accurately?
The control panel shows the temperature detected by the hot tub’s sensor. For extra reassurance, compare it occasionally with a separate waterproof spa thermometer.
Before entering:
- Allow the water to circulate so the temperature is even throughout the tub.
- Check the display and, if available, a separate thermometer.
- Test the water before fully getting in.
- Lower the setting if anyone finds it uncomfortably hot.
If the displayed temperature and thermometer reading differ noticeably, stop using the hot tub and check the manufacturer’s troubleshooting guidance or arrange professional support.
Choosing a Hot Tub with Simple Temperature Control
Reliable controls, effective insulation and a well-fitted cover make it easier to maintain a comfortable temperature throughout the year. When comparing models, also consider seating capacity, jet layout, electrical requirements, access for installation and the aftercare available.
You can explore the full CenturaHeat hot tub collection to compare options for different gardens, households and budgets. More information about the brand and its wider home wellness range is available from CenturaHeat.
Final Answer: What Temperature Should You Set Your Hot Tub To?
For most healthy adults, 37°C to 38°C is the best place to start. Set it slightly cooler, around 35°C to 37°C, during warm weather. In winter, 38°C to 39°C may feel more comfortable, but never exceed the 40°C maximum.
The safest setting also depends on who is using the hot tub and how long they plan to stay in it. Start lower, increase the temperature gradually and leave the water as soon as you feel too hot or unwell.
Frequently Asked Questions
Is 40°C too hot for a hot tub?
40°C is the maximum recommended temperature, not the ideal setting for everyone. If you use a hot tub at 40°C, keep the session short and leave immediately if you feel dizzy, tired, nauseous or overheated.
Is 38°C hot enough for a hot tub?
Yes. A setting of 38°C feels comfortably warm to many adults and is a popular year-round choice.
Is 35°C warm enough for a hot tub?
Yes, particularly in summer. Because 35°C is slightly below normal body temperature, it will feel gentler and may be more comfortable during warm weather.
Should I turn my hot tub temperature down overnight?
Usually, there is little benefit in changing the setting every night if you use the hot tub frequently. A quality cover and steady setting can avoid repeated cooling and reheating. Lowering the temperature may make more sense when the hot tub will not be used for several days.
Does a lower hot tub temperature save electricity?
Generally, yes. A lower difference between the water and outdoor air means less heat is lost. The actual saving depends on the model, insulation, cover, weather and how often the hot tub is used.
Can alcohol affect hot tub safety?
Yes. Alcohol can impair judgement and increase drowsiness, dehydration and the risk of losing consciousness. Avoid drinking alcohol before or during hot tub use.
