What is the discomfort index?
The discomfort index (DI) folds air temperature and relative humidity into one number that is meant to say how oppressive warm weather feels. At the same temperature, humid air keeps sweat from evaporating, so the body cools less effectively and the heat feels heavier. The index captures that interaction. It is a familiar term in Korean summer forecasts and daily living-weather information, but it is an empirical formula, so it will not match every person's experience. Enter a temperature and a humidity and this page returns the number, the level, and the arithmetic behind it.
Which scale is used here. The four levels on this page follow the Korea Meteorological Administration (KMA) living-weather discomfort index. Other countries, private weather services and older textbooks use different thresholds, different level names, or five or six levels. A "high" here is therefore not guaranteed to be called "high" elsewhere, so treat the label as a reading on the KMA scale and not as a universal rating.
The formula
Discomfort index = 0.81 × T + 0.01 × H × (0.99 × T − 14.3) + 46.3, where T is air temperature in °C and H is relative humidity in percent.
It helps to read the formula as two parts. The first, 0.81 × T, is the baseline contribution of temperature if the air were completely dry. The second, 0.01 × H × (0.99 × T − 14.3), is what humidity adds on top. The bracket is positive only when T is above roughly 14.4 °C, which is why the index is a warm-weather tool: on a cool day, extra humidity actually pushes the number down. This page adds a note to any manual result below 20 °C for that reason. Around 30 °C, each extra 10 percentage points of humidity raises the index by about 1.5, which is a handy rule of thumb.
The four levels (KMA scale)
- Below 68: Low. Most people feel comfortable.
- 68 to under 75: Medium. Some people begin to feel discomfort.
- 75 to under 80: High. Described as the point where roughly half of people feel discomfort.
- 80 and above: Very high. Described as the point where almost everyone feels discomfort.
These descriptions of "roughly half" and "almost everyone" are general characterizations that depend on who was surveyed and how, not exact percentages. For the current official wording and thresholds, check the KMA's own living-weather guidance.
Temperature by humidity table
Each value below is calculated from the formula when the page is built, and the label underneath is the KMA level.
| Temp. \ Humidity | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|
| 22 °C | 67.1 (Low) | 67.9 (Low) | 68.6 (Medium) | 69.4 (Medium) | 70.1 (Medium) | 70.9 (Medium) |
| 24 °C | 69.5 (Medium) | 70.5 (Medium) | 71.4 (Medium) | 72.4 (Medium) | 73.3 (Medium) | 74.3 (Medium) |
| 26 °C | 71.9 (Medium) | 73.1 (Medium) | 74.2 (Medium) | 75.4 (High) | 76.5 (High) | 77.7 (High) |
| 28 °C | 74.3 (Medium) | 75.7 (High) | 77.0 (High) | 78.4 (High) | 79.7 (High) | 81.1 (Very high) |
| 30 °C | 76.8 (High) | 78.3 (High) | 79.8 (High) | 81.4 (Very high) | 82.9 (Very high) | 84.5 (Very high) |
| 32 °C | 79.2 (High) | 80.9 (Very high) | 82.6 (Very high) | 84.4 (Very high) | 86.1 (Very high) | 87.9 (Very high) |
| 34 °C | 81.6 (Very high) | 83.5 (Very high) | 85.5 (Very high) | 87.4 (Very high) | 89.3 (Very high) | 91.3 (Very high) |
Two things stand out. First, humidity matters little at 22 °C: going from 40% to 90% humidity moves the value only 3.7 points (67.1 to 70.9). At 34 °C the same humidity change is worth 9.7 points (81.6 to 91.3). Second, at 34 °C even 40% humidity lands at 81.6, already in the Very high band. Dehumidifying pays off most on the hottest days.
Worked examples
- Example 1: 27 °C, 60% humidity. 0.81 × 27 + 0.01 × 60 × (0.99 × 27 − 14.3) + 46.3 gives 75.6, at the start of the High band. A typical day without air conditioning where some people feel clammy.
- Example 2: 32 °C, 75% humidity. The result is 85.3, in the Very high band. At the same 32 °C with only 40% humidity it is 79.2, one band lower.
- Example 3: 30 °C at 40% versus 90%. About 76.8 versus 84.5. Same temperature, but humidity alone moves the reading from High to Very high. That is why a muggy rainy-season day can feel worse than a drier hotter one.
Limits and common misunderstandings
- Wind and sunshine are ignored. Shade versus direct sun, and a breeze versus still air, change how a given reading feels. Other measures such as heat index or feels-like temperature may include extra factors. For cold-weather wind effects, see the wind chill calculator.
- It means little in winter. The formula is built for warm-season discomfort. A low number on a cold day does not mean you will be comfortable.
- People differ. Age, activity level, clothing and how used you are to heat all change the response. Older adults, young children and people with chronic conditions should take extra care even at lower levels.
- It is not a heat warning. Official heat advisories use separate criteria set by local authorities. Check your local weather service.
- Live values are not your room. The city lookup uses temperature and humidity from an external weather service, which can differ from conditions inside your home or office.
Using the result
If you see 75 or more, start with indoor humidity. A dehumidifier or an air conditioner's dry mode that brings humidity down to around 60% can drop the reading by a level at the same temperature. At 80 and above, shorten outdoor exercise, drink water regularly and keep vulnerable people and pets cool and ventilated. To understand condensation and mold risk indoors, the dew point calculator pairs well with this tool, and the world weather page lets you compare other cities. This page is for general reference and is not medical advice. If you feel unwell in the heat, seek proper medical help.
Frequently Asked Questions
I tapped "Use my location" and nothing happened.
Check that you've allowed location access in your browser. If you denied it, search for your city by name instead, or use the manual calculator.
Can I search for a city in my own language?
Searching in English gives the most accurate results (e.g. Seoul, Busan, Incheon). If several matches come back, you can pick the right one by region and country.
Is this the same as "feels like" temperature?
They are related but not identical. The discomfort index only uses temperature and humidity and is mainly a summer measure, while "feels like" figures often include wind or radiation as well.
What happens if I enter humidity above 100%?
Humidity must be between 0 and 100. Anything outside that range shows an error and is not calculated. Temperature is accepted from -50 to 60 °C.
Can I use Fahrenheit?
The formula expects Celsius. Convert first with (°F − 32) × 5/9, then enter the result.