An influential limit. After an influential study in 2010, climate researchers often use a wet bulb temperature of 35 degrees C — roughly equivalent to 95 degrees F at 100% humidity — as an upper limit for human survival and adaptability without cooling.
As a follow-up study of a 2021 investigation , researchers at the University of Roehampton in England conducted a second set of experiments to investigate the upper limit of the thermoneutral zone. They found that the thermoneutral zone's upper limit likely lies between 40℃ (104F) and 50℃ (122F).
On the flip side, “How hot is too hot inside a house?” is equally important to consider. An indoor temperature above 80°F (27°C) can be uncomfortable and may even pose health risks, especially for vulnerable populations like children, the elderly, or those with chronic illnesses.
Sleep experts believe the best temperature for great sleep is between 68-72 degrees Fahrenheit. But in addition to making you uncomfortable and interfering with healthy sleep patterns, being too hot at any time of day or night can cause health risks like dehydration and heat stroke.
The highest environmental temperature humans can survive is 104°F to 122°F (40°C to 50°C). But those temperatures aren't safe. A safe temperature range for prolonged outdoor time is 77°F to 88°F (25°C to 31°C). The heat index accounts for both temperature and humidity.
The best room temperature for sleep is between 66 to 72°F. Your skin should ideally be between 88 to 95°F during sleep. The temperature under your bed covers should be around 90 to 93°F with 40% to 60% humidity.
The World Health Organization recommends a thermostat setting no lower than 68 degrees while you're home. If you have children or seniors in your house, that number increases to at least 70 degrees. If your house is too cold, it can cause problems with blood pressure and circulation, as well as affect your heart rate.
Sleeping too hot
“Heat is a huge disruptor for REM sleep,” Dr. Drerup says. With the heat of the room, your body temperature will also rise, thus undoing the sleep initiation process entirely. If your bedroom temperature is above 70° F, it's too hot.
People who live with long-term health conditions are more vulnerable to the effects of heat, including cardiovascular conditions and diabetes – with the temperature in their homes making it much harder to manage their health.
Home Damage Caused by High Heat
Drywall: Drywall will expand and contract in high heat. This leads to cracks and eventually warping and buckling. Foundation: The soil around your home can become so dry that your foundation shrinks. This may lead to cracks and structural problems down the road.
Heat Index
Caution (80°F – 90°F HI); • Extreme Caution (91°F – 103°F HI); • Danger (103°F – 124°F HI); and, • Extreme Danger (126°F or higher HI).
The conditions that can lead to a wet-bulb temperature of 95 °F vary greatly. With no wind and sunny skies, an area with 50% humidity will hit an unlivable wet-bulb temperature at around 109 °F, while in mostly dry air, temperatures would have to top 130 °F to reach that limit.
A core body temperature of 104 degrees Fahrenheit (40 degrees Celsius) or higher is the main sign of heatstroke. Change in mental state or behavior. Confusion, agitation, slurred speech, irritability, delirium, seizures and coma can all result from heatstroke. Change in sweating pattern.
Most sleep specialists recommend people sleep in a “cool, dark and quiet environment,” typically ranging from about 65 to 75 degrees, said Ronald Chervin, the division chief of the sleep disorders centers and professor of sleep medicine at the University of Michigan, who was not involved in the study.
People aged 65 years or older are more prone to heat-related health problems. Stay cool and hydrated during hot weather. Older adults do not adjust as well as young people to sudden changes in temperature. They are more likely to have a chronic medical condition that changes normal body responses to heat.
More importantly, it's a good idea that you keep your room at a good temperature to avoid any health problems especially for the elderly. As mentioned on the above table, your living room should ideally be between 21°C – 23°C and your bedroom should be between 17°C – 19°C.
An influential limit. After an influential study in 2010, climate researchers often use a wet bulb temperature of 35 degrees C — roughly equivalent to 95 degrees F at 100% humidity — as an upper limit for human survival and adaptability without cooling.
In general, 80 degrees is too hot for a house if people are inside. However, if people aren't home during the day or for vacation during the summer, an indoor temperature of 80 degrees can save energy until you return and lower the temperature.
The best room temperature for sleep is approximately 65 degrees Fahrenheit (18.3 degrees Celsius). This may vary by a few degrees from person to person, but most doctors recommend keeping the thermostat set between 65 to 68 degrees Fahrenheit (15.6 to 20 degrees Celsius) for the most comfortable sleep.
In humid conditions, the air becomes populated by hydrogen and nitrogen as well as oxygen, and our lungs have to work harder to get oxygen from the air. This is part of the reason why we feel so lethargic in humidity, and why physical activity can be especially taxing.