For most people, the ideal indoor temperature falls between 68°F and 72°F (20–22°C) during waking hours. That range balances comfort, health, and energy costs. But the best setting for your home depends on the season, who lives there, and what you’re doing, whether that’s sleeping, working, or keeping a baby comfortable.
The General Comfort Range
The U.S. Department of Energy recommends 68°F in winter and 78°F in summer as starting points that balance comfort with energy efficiency. Those numbers assume you’re adjusting your clothing to the season. In winter, wearing a sweater and long pants at 68°F feels perfectly comfortable. In summer, lighter clothing makes 78°F manageable, especially with a ceiling fan moving air around.
The World Health Organization takes a health-first approach and recommends keeping indoor temperatures at a minimum of 64°F (18°C) in temperate and cold climates to protect against respiratory and cardiovascular problems. That’s a floor, not a target. Most people will want their home a few degrees warmer than that for actual comfort.
Humidity matters too. The EPA recommends keeping indoor relative humidity between 30% and 50%. High humidity makes warm air feel stifling, and low humidity makes cool air feel colder than it is. Keeping humidity in that range also prevents mold growth and discourages dust mites.
Best Temperature for Sleep
Your bedroom should be cooler than the rest of your home. Research published in Frontiers in Neuroscience found that the optimal room temperature for sleep is roughly 66–70°F (19–21°C). At those temperatures, your body can maintain the skin temperature it needs (around 88–95°F at the surface) without fighting against a room that’s too hot or too cold.
This matters because your body naturally drops its core temperature as you fall asleep, and a cool room supports that process. Rooms that are too warm interfere with REM sleep, the phase tied to memory consolidation and dreaming. Rooms that are too cold force your body to work harder to stay warm, which also disrupts deep sleep. If you tend to sleep hot, aim for the lower end of that range and use breathable bedding rather than cranking the air conditioning further down.
Safe Temperatures for Older Adults
Older adults are significantly more vulnerable to cold indoor temperatures. The National Institute on Aging recommends setting the thermostat to at least 68°F for seniors and warns that even mildly cool homes in the 60–65°F range can lead to hypothermia in older adults. This happens because aging reduces the body’s ability to regulate temperature and detect cold.
The risks escalate quickly as temperatures drop. Below about 61°F (16°C), the risk of respiratory diseases increases. Between 48–54°F (9–12°C), the risk of strokes and heart attacks rises sharply. Below 48°F (9°C), hypothermia becomes a real danger. These thresholds are especially important for people over 65 or anyone with heart disease, lung conditions, or circulatory problems. If heating costs are a concern, prioritize warming the rooms where someone spends the most time rather than the entire house.
Nursery Temperature for Babies
Overheating is a known risk factor for sudden infant death, so getting the nursery temperature right matters. Most pediatric guidelines recommend keeping the room between 68°F and 72°F (20–22°C). The CDC advises against letting babies get too hot and recommends checking for signs of overheating like sweating or a hot chest.
A good rule of thumb: dress your baby in one layer more than you’d be comfortable wearing in the same room. Skip hats, heavy blankets, and extra bedding. If the room feels comfortable to you in a t-shirt, it’s likely fine for a baby in a sleep sack.
Keeping Pets Comfortable
Dogs and cats generally do well in the same temperature range humans prefer, but the limits matter if you leave them home alone with the thermostat adjusted. The USDA requires that indoor temperatures for dogs not drop below 45°F for more than four hours and not exceed 85°F for more than four hours. For small breeds, short-haired dogs, puppies, elderly dogs, or sick animals, the minimum is 50°F.
Cats have similar tolerances. If you set the thermostat back while you’re at work, keeping it above 60°F in winter and below 80°F in summer is a safe range for healthy adult pets. Make sure they have access to water and a spot to curl up or stretch out depending on the season.
What Happens When Your Home Is Too Cold
Cold homes aren’t just uncomfortable. They carry measurable health risks that increase as the temperature drops. Here’s how those risks stack up:
- 61–64°F (16–18°C): General discomfort and small health risks for most people
- 54–61°F (12–16°C): Increased risk of respiratory infections and worsening of asthma or COPD
- 48–54°F (9–12°C): Risk of strokes and heart attacks rises, especially in older adults
- Below 48°F (9°C): Hypothermia risk for anyone, particularly dangerous for the elderly and very young
Cold air causes blood vessels to constrict, raising blood pressure and forcing the heart to work harder. It also suppresses the immune response in the airways, making respiratory infections more likely. These effects can develop over hours of exposure, not just in extreme cold snaps.
Saving Energy Without Sacrificing Comfort
Small thermostat adjustments add up. Setting your thermostat back 7–10°F from your normal setting for eight hours a day (while you’re asleep or at work) can cut heating and cooling costs noticeably over a season. A programmable or smart thermostat makes this automatic.
In winter, dropping from 68°F to 62°F while you sleep under warm blankets is reasonable for healthy adults. In summer, letting the house rise to 82–85°F while you’re at work, then cooling it back to 78°F when you get home, saves energy without the discomfort of walking into a hot house. Ceiling fans let you raise the thermostat by about 4°F without feeling warmer, since moving air accelerates sweat evaporation on your skin.
If your home has rooms that are consistently hotter or colder than others, the issue is often poor insulation, leaky windows, or blocked vents rather than the thermostat setting itself. Fixing those problems often does more for comfort than adjusting the temperature.