The answer depends on what you’re measuring. A healthy body temperature for adults falls between 97°F and 99°F (36.1°C to 37.2°C), with the modern average sitting slightly below the old textbook standard of 98.6°F. Your refrigerator should be set between 35°F and 38°F, your freezer at 0°F, and your bedroom at roughly 66°F to 70°F for the best sleep. Here’s a closer look at each one.
Normal Body Temperature
The 98.6°F figure that most of us grew up with dates back to a 19th-century German study and has stuck around ever since. But a large analysis of American health data spanning nearly 200 years found that average body temperature has been dropping by about 0.05°F per decade. The likely explanation: lower rates of chronic infection and inflammation compared to earlier centuries. Today, a normal oral reading for a healthy adult is closer to 97.5°F to 98.3°F.
Your temperature also shifts throughout the day by as much as 1°F to 2°F. It tends to be lowest in the early morning and peaks in the late afternoon or early evening, roughly 10 hours after you wake up. Exercise, stress, ovulation, heavy meals, and even hot weather can push it higher without anything being wrong.
Where you take your temperature matters too. Rectal readings run about 0.7°F to 0.8°F higher than armpit readings, and oral readings fall somewhere in between. If you’re comparing numbers from different methods, keep those offsets in mind.
When a Fever Starts
A temperature at or above 100.4°F (38°C) is the widely accepted threshold for a fever. The CDC uses this same cutoff for reporting illness. Below that, readings in the 99°F to 100.3°F range are sometimes called a low-grade fever, though they can also just reflect normal daily fluctuation or recent physical activity.
Fever itself is your immune system’s response to infection. It’s not inherently dangerous in most adults until it climbs above 103°F or persists for more than a few days. In infants under three months, any reading of 100.4°F or higher is treated more urgently because their immune systems are still developing.
When Body Temperature Drops Too Low
On the other end of the spectrum, a core body temperature below 95°F (35°C) is classified as hypothermia. It progresses in stages:
- Mild (95°F to 89.6°F): shivering, confusion, difficulty with fine motor tasks like zipping a jacket.
- Moderate (89.6°F to 82.4°F): shivering may stop, drowsiness sets in, heart rate slows.
- Severe (below 82.4°F): loss of consciousness, dangerously slow heartbeat, risk of cardiac arrest.
Hypothermia doesn’t require arctic conditions. Prolonged exposure to temperatures in the 50s or 60s, especially with wet clothing or wind, can bring on mild hypothermia in vulnerable people like older adults or young children.
Ideal Room Temperature for Sleep
Your body cools itself slightly as part of the process of falling asleep, and a room that’s too warm interferes with that drop. Sleep research consistently points to a range of about 66°F to 70°F (19°C to 21°C) as the sweet spot. At those temperatures, your skin settles into a comfortable microclimate between roughly 88°F and 95°F under the covers, which supports deeper, less fragmented sleep.
If your bedroom regularly sits above 75°F at night, you’re more likely to wake during lighter sleep stages and spend less time in the deep, restorative phases. A fan, lighter bedding, or simply cracking a window can make a meaningful difference if air conditioning isn’t an option.
Safe Refrigerator and Freezer Settings
Your refrigerator should stay between 35°F and 38°F, with 37°F being the ideal target. The key rule: never let any section climb above 40°F, because bacteria that cause foodborne illness begin multiplying rapidly above that point. Your freezer should be set to 0°F, which keeps food safe indefinitely (though quality degrades over time).
An inexpensive appliance thermometer placed in the center of the fridge is the most reliable way to verify your settings, since the built-in dial on many refrigerators isn’t always accurate.
Safe Cooking Temperatures
Internal temperature is the only reliable way to know meat is safe to eat. Color and texture can be misleading. These are the minimum targets measured with a food thermometer at the thickest part:
- Poultry (chicken, turkey, duck): 165°F (74°C), whether it’s a whole bird, ground poultry, or stuffing cooked inside.
- Ground beef, pork, or lamb: 160°F (71°C). Grinding meat spreads bacteria throughout, so it needs a higher temperature than whole cuts.
- Pork chops, steaks, and roasts: 145°F (63°C), followed by a three-minute rest before cutting. During that rest, the internal temperature stays high enough to finish killing harmful bacteria.
- Beef and lamb steaks and roasts: 145°F (63°C) with a three-minute rest for medium-rare and above.
Dangerous Heat Indoors
There’s no single indoor temperature that’s universally “dangerous” because humidity, air movement, physical activity, and individual health all play a role. A dry 90°F room with a fan is far less risky than a humid 85°F room with no air circulation. Occupational safety guidelines use a measurement called the wet bulb globe temperature, which combines air temperature, humidity, sunlight, and wind into one number, to assess heat risk more accurately than a thermometer alone.
For practical purposes, indoor temperatures above 80°F become uncomfortable for most people at rest, and sustained exposure above 90°F with high humidity raises the risk of heat exhaustion, especially for older adults, young children, and anyone on medications that affect sweating or blood flow. Staying hydrated and maintaining air circulation are the two most effective protective steps when cooling a room isn’t possible.