Feels Like Temperature Calculator

Q: At what heat index is it dangerous to be outside?

Risk climbs in steps: Caution: at a heat index of 80–90°F, fatigue is possible with prolonged exposure and/or physical activity. 2 That is about 27–32°C. Extreme Caution: at 90–103°F, heat stroke, heat cramps, or heat exhaustion are possible with prolonged exposure and/or physical activity. 2 That is about 32–39°C. Danger: at 103–124°F, heat cramps or heat exhaustion are likely, and heat stroke is possible with prolonged exposure and/or physical activity. 2 That is about 39–51°C. Extreme Danger: at 125°F or higher, heat stroke is highly likely. 2 That is about 52°C and above. Hard work or sports raise the risk at every step.

Q: How fast can you get frostbite from wind chill?

It depends on how low the wind chill goes: -10 to -27: risk of frostbite if outdoors for long periods without adequate protection 6 -28 to -39: exposed skin can freeze in 10 to 30 minutes 6 -40 to -47: exposed skin can freeze in 5 to 10 minutes 6 -48 to -54: exposed skin can freeze in 2 to 5 minutes 6 -55 or colder: exposed skin can freeze in less than 2 minutes 6 In sustained winds over 50 km/h, frostbite can occur faster than these times. 6 The body parts most often affected are the nose, ears, toes, cheeks, chin, and fingers. 10

Q: Does wind chill affect car engines, pipes, or water freezing?

No. Wind chill applies only to people and animals. 5 The only effect it has on things like car radiators and water pipes is to cool them more quickly to the air temperature. 5 They will not cool below the actual air temperature. 5 For example, if the air temperature is -20°C and the wind chill is -30, objects outside will only cool to -20°C, not -30°C. 6 Wind can still make a pipe reach the air temperature, and freeze, sooner on a windy night.

Q: Does standing in the sun change the feels like temperature?

Yes, a lot. Heat index numbers assume you are in the shade . Heat index values were devised for shady, light-wind conditions, and full sunshine can raise them by up to 15°F . 3 That is about 8°C. So a heat index of 38°C in the shade can feel like up to 46°C standing in full sun. Shade, hats, and light clothes make a real difference.

Feels Like Temperature Calculator

Introduction

The number on a thermometer does not always match how the air feels on your skin. On a muggy summer day, 32°C can feel like 41°C. On a windy winter morning, 0°C can feel like -8°C. This Feels Like Temperature Calculator shows you that real number.

Just type in three things: the air temperature, the relative humidity, and the wind speed. The tool picks the right formula for you. When it is hot and damp, it uses the NOAA Heat Index, because sweat cannot dry as fast in wet air. When it is cold and breezy, it uses the NWS Wind Chill formula, because wind pulls heat away from your body. If the weather is mild, no change is needed, and the calculator says so.

You get your apparent temperature in °C, °F, and K, plus a comfort level like "Warm," "Cold," or "Extreme Heat." You also see every math step, a chart, and a table that shows how the feels-like number moves as humidity or wind changes.

Use it to plan a run, a hike, a work shift outside, or to know when heat or cold could turn risky. It takes seconds, and it helps you dress right and stay safe.

How to use our Feels Like Temperature Calculator

Enter the air temperature, the relative humidity, and the wind speed. The calculator shows the feels like temperature (also called apparent temperature), how much warmer or colder it feels than the real reading, the formula used, a comfort level, a chart, and a step-by-step solution.

Actual Temperature: Type the air temperature measured in the shade. Pick °C, °F, or K from the drop-down next to the box. If you change the unit, your number is converted for you.

Relative Humidity (%): Type how moist the air is, from 0 to 100. High humidity makes hot days feel hotter, so this drives the heat index result.

Wind Speed: Type the steady wind speed and choose km/h, mph, m/s, or knots. Wind matters most on cold days, since it drives the wind chill result.

Calculate and Reset: Results update as you type, but you can click Calculate at any time. Click Reset to go back to the starting values.

What Is Feels Like Temperature?

The feels like temperature (also called apparent temperature) is how hot or cold the air really feels on your skin. A thermometer only reads the air temperature. But your body also reacts to humidity and wind. That is why 32°C can feel like 41°C on a sticky day, and 0°C can feel like -8°C when the wind blows hard.

Heat Index: Why Humidity Makes Heat Worse

Your body cools itself by sweating. When sweat dries off your skin, it takes heat with it. But when the air is already full of water vapor (high humidity), sweat dries slowly. So your body holds on to heat and you feel hotter than the real temperature.

The heat index is the number weather services use to show this. It comes from a regression equation published in 1990 by Lans P. Rothfusz of the National Weather Service.⁴ This calculator uses it when the air is 27°C or warmer, at any humidity.

Wind Chill: Why Wind Makes Cold Worse

A thin layer of warm air sits right against your skin. Wind blows that layer away, so your body loses heat faster.⁶ The wind chill formula from the U.S. National Weather Service shows how cold that feels. The NWS defines wind chill only for temperatures at or below 50°F and wind speeds above 3 mph.⁵ That is about 10°C and 5 km/h, and this calculator uses the same limits.

When the weather is mild (not hot and humid, and not cold and windy), no change is made. The feels like temperature is just the air temperature.

Comfort Levels

Feels Like	How It Feels
Below -25°C	Extreme cold: frostbite risk, cover all skin
-25°C to 0°C	Very cold to cold: cover skin
0°C to 10°C	Cool: a jacket helps
10°C to 20°C	Comfortable
20°C to 27°C	Warm
27°C to 35°C	Hot: drink water, take breaks
35°C to 45°C	Very hot: heat cramps and heat exhaustion are possible
Above 45°C	Extreme heat: heat stroke risk, stay indoors

Why It Matters

Weather warnings, school sports rules, and work safety plans use feels like temperature, not the plain thermometer reading. It is a better guide for real risk. On hot days, high heat index numbers warn of heat exhaustion and heat stroke. On cold days, low wind chill numbers warn of frostbite and hypothermia.

Good To Know

Heat index values were devised for shady, light-wind conditions, and full sunshine can raise them by up to 15°F.³ That is about 8°C.
The NWS wind chill formula works out the wind at an average face height of 5 feet from readings taken at the standard anemometer height of 33 feet.⁵ Those heights are about 1.5 m and 10 m, so the wind right around you may feel different.
Be even more cautious with children, older adults, and people in poor health.⁵
Wind chill applies only to people and animals.⁵ Objects such as water pipes cool faster in the wind, but never below the air temperature.⁵

Formulas used

Simple Heat Index Screen (NOAA) ¹

HI_{simple} = 0.5\left[T_F + 61 + (T_F - 68)(1.2) + RH(0.094)\right]

Heat Index — Rothfusz Regression (NOAA) ⁴

HI = -42.379 + 2.04901523\,T_F + 10.14333127\,RH - 0.22475541\,T_F\,RH - 6.83783 \times 10^{-3}\,T_F^2 - 5.481717 \times 10^{-2}\,RH^2 + 1.22874 \times 10^{-3}\,T_F^2 RH + 8.5282 \times 10^{-4}\,T_F\,RH^2 - 1.99 \times 10^{-6}\,T_F^2 RH^2

Low-Humidity Adjustment (RH < 13%, 80°F ≤ T ≤ 112°F) ¹

HI_{adj} = HI - \frac{13 - RH}{4}\sqrt{\frac{17 - |T_F - 95|}{17}}

High-Humidity Adjustment (RH > 85%, 80°F ≤ T ≤ 87°F) ¹

HI_{adj} = HI + \frac{RH - 85}{10}\cdot\frac{87 - T_F}{5}

Wind Chill (NWS) ⁵

WC = 35.74 + 0.6215\,T_F - 35.75\,v^{0.16} + 0.4275\,T_F\,v^{0.16}

Formula Selection Logic

T_{feels} = \begin{cases} HI, & T \ge 27^\circ\text{C} \\ WC, & T \le 10^\circ\text{C} \text{ and } v > 3\ \text{mph} \\ T, & \text{otherwise} \end{cases}

Temperature Unit Conversions ¹²

T_F = T_C \times \frac{9}{5} + 32, \qquad T_C = (T_F - 32)\times\frac{5}{9}, \qquad T_K = T_C + 273.15

Difference from Actual Temperature

\Delta T = T_{feels} - T_{actual}

Frequently asked questions

What humidity level makes it feel hotter than it is?

On a day of 27°C or warmer, this calculator applies the heat index at any humidity. In drier air, sweat evaporates faster, and the heat index can even come out below the air temperature.² Above 60%, the gap grows quickly.

At 32°C (90°F):

40% humidity feels like about 32°C
60% humidity feels like about 37°C
80% humidity feels like about 44°C

At what heat index is it dangerous to be outside?

Risk climbs in steps:

Caution: at a heat index of 80–90°F, fatigue is possible with prolonged exposure and/or physical activity.² That is about 27–32°C.
Extreme Caution: at 90–103°F, heat stroke, heat cramps, or heat exhaustion are possible with prolonged exposure and/or physical activity.² That is about 32–39°C.
Danger: at 103–124°F, heat cramps or heat exhaustion are likely, and heat stroke is possible with prolonged exposure and/or physical activity.² That is about 39–51°C.
Extreme Danger: at 125°F or higher, heat stroke is highly likely.² That is about 52°C and above.

Hard work or sports raise the risk at every step.

How fast can you get frostbite from wind chill?

It depends on how low the wind chill goes:

-10 to -27: risk of frostbite if outdoors for long periods without adequate protection⁶
-28 to -39: exposed skin can freeze in 10 to 30 minutes⁶
-40 to -47: exposed skin can freeze in 5 to 10 minutes⁶
-48 to -54: exposed skin can freeze in 2 to 5 minutes⁶
-55 or colder: exposed skin can freeze in less than 2 minutes⁶

In sustained winds over 50 km/h, frostbite can occur faster than these times.⁶ The body parts most often affected are the nose, ears, toes, cheeks, chin, and fingers.¹⁰

Does wind chill affect car engines, pipes, or water freezing?

No. Wind chill applies only to people and animals.⁵ The only effect it has on things like car radiators and water pipes is to cool them more quickly to the air temperature.⁵ They will not cool below the actual air temperature.⁵

For example, if the air temperature is -20°C and the wind chill is -30, objects outside will only cool to -20°C, not -30°C.⁶ Wind can still make a pipe reach the air temperature, and freeze, sooner on a windy night.

Why does 30°C feel hotter in Florida than in Arizona?

Humidity. Over a year, Miami averages 82% relative humidity in the morning and 61% in the afternoon.¹⁵ In air that moist, sweat cannot evaporate well. The heat stays in your body and 30°C can feel like about 35–38°C.

Arizona air is dry: Phoenix averages 46% relative humidity in the morning and 23% in the afternoon.¹⁵ Sweat dries almost instantly and carries heat away, so 30°C can feel close to 30°C, or even a bit cooler.

Is there a wind chill when it is above 50°F (10°C)?

No. The NWS defines wind chill only for temperatures at or below 50°F and wind speeds above 3 mph.⁵ That is about 10°C and 5 km/h. Outside those limits, no wind chill is given.

Wind can still feel cool on a mild day, especially if your skin is damp. Environment and Climate Change Canada does not show a wind chill when the temperature is above zero, because there is no risk of frostbite then, however windy it is.⁶

Does standing in the sun change the feels like temperature?

Yes, a lot. Heat index numbers assume you are in the shade. Heat index values were devised for shady, light-wind conditions, and full sunshine can raise them by up to 15°F.³ That is about 8°C.

So a heat index of 38°C in the shade can feel like up to 46°C standing in full sun. Shade, hats, and light clothes make a real difference.

What temperature is comfortable for most people?

For offices, OSHA recommends temperature control in the range of 68–76°F and humidity control in the range of 20%–60%.¹⁶ That is about 20–24°C.

Below 10°C most people want a jacket. Above 27°C most people start to feel hot and need water and breaks.

Can the feels like temperature be lower than the actual temperature in summer?

Yes, when the air is very dry. When the relative humidity is low, the heat index can be lower than the air temperature.² For example, at 100°F and 15% relative humidity the heat index is 96°F.² At 35°C and 15% humidity it works out to about 33°C.

This calculator applies the heat index at any humidity on days of 27°C or warmer, so in air that dry it shows a feels-like temperature below the air temperature.

Which is more dangerous, high heat index or low wind chill?

Both can kill. In a study of more than 74 million deaths in 13 countries, more deaths were caused by cold (7.29% of all deaths) than by heat (0.42%).¹³ Heat stroke is the faster danger: body temperature can rise to 106°F or higher within 10 to 15 minutes.¹⁴

Cold usually takes longer to become deadly, and warm clothes are an easy fix. But hypothermia can occur even at cool temperatures above 40°F if a person becomes chilled from rain, sweat, or submersion in cold water.¹⁰ That is above about 4°C.

How much does humidity add to the heat index at 40°C?

At 40°C (104°F) the jump is large:

40% humidity → feels like about 48°C.
50% humidity → feels like about 55°C.
60% humidity → feels like about 63°C.
70% humidity → feels like about 72°C.

The NWS classes a heat index of 125°F or higher as Extreme Danger, where heat stroke is highly likely.² That is about 52°C. The Rothfusz regression is not valid for extreme temperature and relative humidity conditions beyond the range of data considered by Steadman.¹

What is the difference between heat index and wet bulb temperature?

Both mix heat and humidity, but they answer different questions.

Heat index tells you how hot the air feels to a person in the shade.³ It is reported in the same range as normal temperatures.

Wet bulb temperature is the lowest temperature that can be reached by evaporating water into the air.⁸ Scientists have argued that a wet bulb temperature above 35°C for extended periods would cause hyperthermia, because the body could no longer get rid of its metabolic heat.⁹

Why does wind chill use a 3 mph minimum?

The 2001 wind chill model is for a person walking into the wind, and its still-air reference assumes a minimum air speed of 1.34 m/s, the average walking speed of American pedestrians.⁷ That is about 3 mph. The NWS set the calm-wind threshold at 3 mph and defines wind chill only for wind speeds above it.⁵

How do I dress for a cold wind chill?

Wear several layers of loose-fitting, lightweight, warm clothing, because the air trapped between the layers insulates you.¹¹ Cover your skin:

Base layer: wool or synthetic, not cotton (cotton holds sweat)
Middle layer: fleece or down to trap warm air
Outer layer: windproof shell to block the chill
Cover: hat, gloves, and something over your nose and cheeks

Wind chill is based on the rate of heat loss from exposed skin caused by wind and cold.⁵ That is why a windproof shell and covered skin matter most.

Do humidity and wind matter at the same time?

Rarely for the official formulas. Heat index uses temperature and humidity only. Wind chill uses temperature and wind only. Each formula runs in its own temperature range, so they do not overlap.

In real life a breeze does help on a hot day by speeding up sweat evaporation. The heat index model assumes a wind of 5 knots, so a stronger breeze is not counted.⁴

Sources

The Heat Index Equation. NOAA National Weather Service, Weather Prediction Center. Accessed September 29, 2026.

What is the heat index? NOAA National Weather Service, Amarillo, TX Weather Forecast Office. Classification table. Accessed September 29, 2026.

Heat Forecast Tools. NOAA National Weather Service. Heat Index. Accessed September 29, 2026.

Rothfusz LP. The Heat Index "Equation" (or, More Than You Ever Wanted to Know About Heat Index). Technical Attachment SR 90-23. NOAA National Weather Service, Southern Region Headquarters. 1990;pp. 1-2. Accessed September 29, 2026.

Understanding Wind Chill. NOAA National Weather Service. Wind Chill FAQ. Accessed September 29, 2026.

Wind chill and the Wind Chill Index. Environment and Climate Change Canada. Your safety risk for wind chill exposure. Accessed September 29, 2026.

Osczevski R, Bluestein M. The New Wind Chill Equivalent Temperature Chart. Bulletin of the American Meteorological Society. 2005;86(10):1453-1458. doi:10.1175/BAMS-86-10-1453. Accessed September 29, 2026.

Glossary: Wet-Bulb Temperature. NOAA National Weather Service. Accessed September 29, 2026.

Sherwood SC, Huber M. An adaptability limit to climate change due to heat stress. Proceedings of the National Academy of Sciences. 2010;107(21):9552-9555. doi:10.1073/pnas.0913352107. Accessed September 29, 2026.

Preventing Hypothermia. Centers for Disease Control and Prevention. Accessed September 29, 2026.

Wind Chill Questions. NOAA National Weather Service. Dress for safety. Accessed September 29, 2026.

NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically. National Institute of Standards and Technology. Special Publication 811, App. B.8 (degree Celsius, degree Fahrenheit). Accessed September 29, 2026.

Gasparrini A, Guo Y, Hashizume M, Lavigne E, Zanobetti A, Schwartz J, et al. Mortality risk attributable to high and low ambient temperature: a multicountry observational study. The Lancet. 2015;386(9991):369-375. doi:10.1016/S0140-6736(14)62114-0. Accessed October 7, 2026.

Heat-related Illnesses. CDC, National Institute for Occupational Safety and Health. Heat stroke. Accessed October 7, 2026.

Comparative Climatic Data: Average Relative Humidity, data through 2023. NOAA National Centers for Environmental Information. Miami, FL and Phoenix, AZ, annual morning and afternoon. Accessed October 7, 2026.

Reiteration of Existing OSHA Policy on Indoor Air Quality: Office Temperature/Humidity and Environmental Tobacco Smoke. Occupational Safety and Health Administration. 2003;Office Temperature/Humidity. Accessed October 9, 2026.

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