The Central Weather Administration (CWA) calculates apparent temperature (feels-like temperature) from three numbers: air temperature, relative humidity and wind speed. The formula cites a 1984 study by Steadman and does not include sunshine. According to the CWA reference table, in a light breeze of 2.5 m/s, air at 30°C feels like about 33°C at 70% relative humidity and can reach 35°C at 100% humidity. The higher the humidity, the muggier it feels, which is why 30 degrees can feel like 35.
This article collects the formula, variables and reference tables from the CWA document on its apparent-temperature forecast service (體感溫度預報服務), explains how apparent temperature differs from the US Heat Index (commonly translated into Chinese as 酷熱指數, the term this article uses) and from the heat information color signals, and finishes with how to use it for commuting and choosing what to wear. To check today's apparent temperature, use this site's commute outfit and umbrella decision helper or Taiwan weather and UV by county.
What apparent temperature is, and what air temperature is
The CWA document first defines air temperature: in meteorology, it is the temperature of the atmosphere measured by a thermometer placed 1.25 to 2.00 meters above the ground, well ventilated and out of direct solar radiation. Apparent temperature is meant to reflect how the human body feels the air temperature, and that sensation comes mainly through the skin.
The same document explains that apparent temperature differs with humidity, wind speed, direct sunshine and the body's basal metabolic rate. It says that sunshine and metabolic rate are hard to calculate quantitatively, so the formula takes into account the effects of humidity and wind speed. The principle is this: the higher the humidity, the harder it is for the skin surface to shed heat, so you feel a temperature higher than the actual air temperature; stronger wind speeds up heat loss from the skin, so you feel a temperature lower than the air temperature. An apparent temperature above the air temperature means the environment feels hotter; below the air temperature, it feels colder.
The CWA formula and its three variables
The document states that the apparent temperature the CWA provides applies to outdoor environments that are ventilated and sheltered (通風有遮蔽), that it considers the weather elements of air temperature, humidity and wind speed, and that the formula cites a study published by Steadman, R.G. in 1984, A universal scale of apparent temperature. This formula comes from the explanatory document on the apparent-temperature forecast service of the CWA (formerly the Central Weather Bureau, 中央氣象局). The document carries no date and its text still uses the name "Central Weather Bureau", so it is evidently from before the renaming in 2023. The current product description document for the 368 township forecasts (January 2026 edition) does not state how apparent temperature is calculated, and this article did not find any announcement of a switch to a different formula. The formula is:
- Apparent temperature = 1.04 × T + 0.2 × e − 0.65 × V − 2.7
- e = RH ÷ 100 × 6.105 × exp(17.27 × T ÷ (237.7 + T))
- T is air temperature (°C), e is water vapor pressure (hPa), V is wind speed (meters per second) and RH is relative humidity (%)
Three things follow from the formula. First, the coefficient on air temperature is 1.04, so apparent temperature roughly follows air temperature. Second, the vapor pressure e rises with both humidity and air temperature: the higher the temperature and the humidity, the more is added, and that is where the muggy feeling comes from. Third, every additional 1 meter per second of wind lowers apparent temperature by 0.65 degrees; the formula also subtracts a fixed 2.7, so in low-temperature, dry, windless conditions apparent temperature will be slightly below air temperature.
Pay attention to the words "ventilated and sheltered". This formula does not account for direct sun, and the document states plainly that direct sunshine raises apparent temperature. Standing on asphalt at noon, what you actually feel will be hotter than the forecast apparent temperature.
CWA reference table: why 30 degrees feels like 35
The CWA document includes two simple reference tables. Table 1 fixes the wind speed at 2.5 m/s (about force 2 wind) to show the effect of humidity at high temperatures; Table 2 fixes the relative humidity at 70% to show the effect of wind speed at low temperatures. This article excerpts a few cells below, with values taken directly from those tables.
| Condition | Air temperature | Humidity or wind speed | Apparent temperature | Source |
|---|
| Wind speed 2.5 m/s | 30°C | Relative humidity 30% | 29°C | CWA Table 1 |
| Wind speed 2.5 m/s | 30°C | Relative humidity 50% | 31°C | CWA Table 1 |
| Wind speed 2.5 m/s | 30°C | Relative humidity 70% | 33°C | CWA Table 1 |
| Wind speed 2.5 m/s | 30°C | Relative humidity 90% | 34°C | CWA Table 1 |
| Wind speed 2.5 m/s | 30°C | Relative humidity 100% | 35°C | CWA Table 1 |
| Wind speed 2.5 m/s | 33°C | Relative humidity 85% | 39°C | CWA Table 1 and the worked example in the text |
| Relative humidity 70% | 10°C | No wind | 9°C | CWA Table 2 |
| Relative humidity 70% | 10°C | Wind speed 6 m/s (about force 4 wind) | 6°C | CWA Table 2 and the worked example in the text |
| Relative humidity 70% | 10°C | Wind speed 10 m/s | 3°C | CWA Table 2 |
So "30 degrees feels like 35" is not an illusion: humidity pushes up the vapor pressure term. According to Table 1, at the same air temperature of 30 degrees, as relative humidity rises from 30% to 100%, apparent temperature rises from 29 degrees to 35 degrees. The document also warns that high temperature combined with high humidity raises the chance of discomfort and heat stroke, while low temperature combined with strong wind may cause body temperature to drop quickly. For converting wind force levels, see this Beaufort wind scale comparison.
How it differs from the heat index and the heat signals
The CWA document lists several similar indices. The Heat Index (commonly translated into Chinese as 酷熱指數, the term this article uses) issued by the US National Oceanic and Atmospheric Administration and the Humidex of the Canadian national environment department (環境部) consider only air temperature and relative humidity; the Wind Chill issued in the US and Canada considers only air temperature and wind speed. The document says these indices apply to different temperature ranges and seasons. Judging from the formulas, the CWA's apparent temperature puts humidity and wind speed into a single equation (this article's own summary).
Another thing often confused with it is the CWA's heat information (高溫資訊) color signals. The heat information page states that yellow means air temperature reaching 36 degrees or above; orange means air temperature of 36 degrees or above lasting 3 days or more, or reaching 38 degrees or above; red means air temperature of 38 degrees or above lasting 3 days or more. The signals look at air temperature, not apparent temperature, so a day with an apparent temperature of 38 degrees does not necessarily have a signal. For what the signals mean and the recommended actions at each level, see the standards for the yellow, orange and red heat information signals; winter low-temperature advisories follow a different set of standards, covered in how to read the yellow, orange and red low-temperature advisories.
Where to check, and how to use it for commuting and clothing
The CWA's apparent-temperature forecast covers counties and cities, townships, Hakka villages (客庄), indigenous townships (原鄉), forest recreation areas and other areas. It provides apparent temperature every 3 hours for the next 3 days, plus the highest and lowest apparent temperature for the week. According to the CWA product description document for the 368 township forecasts (version of January 6, 2026), township forecasts provide apparent temperature hourly for the next 1 day and every 3 hours for the next 3 days, plus the highest and lowest apparent temperature every 12 hours for the next 7 days. They are issued 4 times a day, at 5:30, 11:30, 17:30 and 23:30, and may be updated immediately when actual weather differs greatly from the forecast.
The following is the way of using it that this article suggests:
- Look at your own township, not just the county. Township forecasts include apparent temperature, and the figures for the mountains and the plains of the same county may differ.
- For commuting, read the 3-hour cell. Apparent temperature in the morning and evening of the same day can differ quite a bit, and an outer layer that is easy to put on and take off is more useful than looking only at the daily high.
- On a scooter, add the wind yourself. The forecast uses ambient wind speed; the headwind you face while riding is not in the forecast. By the formula, the stronger the wind, the lower the apparent temperature, so in winter you can wear one more layer than the forecast suggests.
- Add more for sun. The formula does not include sunshine; when walking on unshaded roads at noon, take UV into account as well, which you can check with the real-time UV index lookup.
- Indoors is a different matter. The apparent-temperature formula is for outdoor use, and indoor mugginess is mainly a humidity problem; see what indoor humidity counts as damp and the difference between the air conditioner dry mode and cool mode.
FAQ
Who measures apparent temperature? Is there an instrument?
There is no apparent-temperature thermometer. It is a number calculated by plugging three observed or forecast values, air temperature, relative humidity and wind speed, into the formula the CWA publishes.
The forecast says an apparent temperature of 35 degrees, but I feel hotter than that in the sun. Why?
The CWA formula applies to outdoor environments that are ventilated and sheltered and does not include direct sunshine; the document states that sunshine raises apparent temperature. It is normal to feel hotter when you are in the sun.
Why is apparent temperature sometimes lower than air temperature?
The formula has two subtracted terms, 0.65 × wind speed and a fixed 2.7. When humidity is low and the wind is strong, the vapor pressure term adds little and the subtracted terms take away more, so apparent temperature falls below air temperature. CWA Table 2 shows that at an air temperature of 10 degrees, humidity of 70% and wind speed of 6 meters per second, apparent temperature is only 6 degrees.
Can I calculate it myself?
Yes. The formula and units are in the CWA document. Note that wind speed is in meters per second, not kilometers per hour, and that relative humidity is plugged into RH as a percentage number.
Last updated: 2026-10-30
This article was compiled by SOSfix editors from public information and is for general reference only. For actual forecasts and heat warnings, rely on the latest issuance from the Central Weather Administration; if you feel unwell, see a doctor.
Sources
- Central Weather Bureau (now the Central Weather Administration), Weather Service Series (12): Apparent Temperature Forecast Service (in Chinese; 中央氣象局氣象服務系列（十二）：體感溫度預報服務; the document carries no date and its text uses the pre-renaming name "Central Weather Bureau"; accessed 2026-10-30): definitions of air temperature and apparent temperature, influencing factors, applicability to outdoor ventilated and sheltered environments, the Steadman 1984 formula and the units of its variables, the differences among Heat Index, Humidex and Wind Chill, the reference values in Table 1 and Table 2, the worked examples of 33 degrees at 85% humidity giving 39 degrees and 10 degrees at 6 meters per second giving 6 degrees, and the forecast coverage and time steps.
- Central Weather Administration product description document: Forecasts, refined weather forecasts, 368 township forecasts (in Chinese; 中央氣象署產品說明文件; last modified 2026-01-06): hourly and 3-hourly apparent temperature and 12-hourly highest and lowest apparent temperature, the 4 daily issue times, and the update frequency; this document does not state how apparent temperature is calculated.
- Central Weather Administration: heat information page (in Chinese; 高溫資訊頁面; accessed 2026-10-30): the yellow, orange and red signals are based on air temperatures of 36 and 38 degrees and the number of days they last.
- Central Weather Bureau, Meteorological Common Knowledge Q&A (in Chinese; 氣象常識問答集; March 2020 edition): the items in township forecasts and refined forecasts include apparent temperature, relative humidity, wind direction and speed, and comfort level.
