Apparent Temperature Calculator

Estimate how hot or cold the air actually feels once humidity, wind and sunlight are taken into account. Supply the temperature, the relative humidity, the wind speed and the solar radiation, and the page returns a feels-like figure alongside the method it used.

Three Methods, Picked Automatically

The page does not blend methods into a single formula. It works out which conditions apply and then chooses one of three recognised calculations, adding a sunlight adjustment on top of whichever one wins. The comparison block below the result lists the other figures so you can see how far apart they are.

• Inputs are converted before any formula runs. A Celsius temperature is turned into Fahrenheit, and a wind speed in kilometres per hour or metres per second is turned into miles per hour.
• The heat-index method is used when the air is at least 80 degrees Fahrenheit and the relative humidity is at least 40 percent. It is the Rothfusz regression, with a subtraction for very dry conditions and an addition for very humid ones at the top of its range.
• The wind-chill method applies when the temperature is 50 degrees Fahrenheit or below and the wind is at least 3 miles per hour. Outside either condition it is not calculated at all.
• When neither extreme fits, the page falls back to the Australian apparent temperature, which folds temperature, humidity and wind into one expression and works across mild conditions.
• Vapour pressure, the ingredient the fallback needs, is derived from the temperature and the relative humidity before the fallback is calculated.
• A solar term is then added to the chosen figure: the radiation value in watts per square metre multiplied by two hundredths, so a bright day lifts the feels-like number by several degrees.
• The comparison block lists whichever of the heat index and wind chill were computed, always lists the Australian value, and finishes with the final figure after the solar adjustment.

Working Out a Feels-Like Figure

1. Enter the air temperature and choose whether it is in Fahrenheit or Celsius.
2. Enter the relative humidity as a percentage between zero and one hundred.
3. Enter the wind speed and pick its unit. The page converts it internally, so any of the offered units will do.
4. Set the solar radiation in watts per square metre, or choose one of the presets for shade, a cloudy day, a sunny day or full sun.
5. The result updates as you edit, so there is no separate submit step required.
6. Read the feels-like panel first, then the method line underneath, which names the calculation that was applied and explains the conditions it represents.
7. Check the comparison block to see the values the other methods would have produced, and note the solar effect line when radiation is greater than zero.

Three Sets of Conditions, Three Different Methods

Using the page's own defaults, 75 degrees Fahrenheit, 50 percent humidity, a 5 mile-per-hour wind and 300 watts per square metre of solar radiation, the tool settles on the mild-weather fallback rather than either extreme.

• For the default case neither the heat index nor the wind chill qualifies: the temperature is above 50 but below 80, so the Australian formula is applied.
• That fallback works out to about 74.3 degrees before sunlight, and the solar term adds 6 degrees, leaving a feels-like reading of 80.3 degrees Fahrenheit, or 26.9 degrees Celsius.
• Raising the temperature to 95 degrees with 60 percent humidity and 600 watts per square metre switches the page to the heat index, which returns about 113.1 degrees before the solar term and 125.1 degrees after it.
• Cooling the air to 30 degrees with a 10 mile-per-hour wind and no sunlight switches it to wind chill, which returns about 21.3 degrees, and with zero radiation the added solar term is nothing.
• A middle case such as 85 degrees at only 30 percent humidity qualifies for neither extreme: the heat index needs at least 40 percent humidity and the wind chill needs 50 degrees or below, so the Australian formula is used again.
• The comparison block is the quickest way to see the spread, because it prints the heat index and wind chill only when they were actually calculated.

Ways to Describe How the Weather Feels

Alternative	Notes
Heat index	Built for warm, humid air, where sweat evaporates slowly and the body struggles to shed heat. It assumes shade and light wind, so a direct-sun figure will read higher than it reports.
Wind chill	Built for cold, windy air, where moving air strips heat from exposed skin faster than still air would. It is entirely about the skin, so wind chill has no meaning on a thermometer in the sun or on a sheltered surface.
Australian apparent temperature	A single expression that covers the middle ground where neither of the extreme methods applies, taking temperature, humidity and wind together. It is the reasonable default across ordinary conditions.
Plain air temperature	The reading on the thermometer, with no adjustment for wind, moisture or sun. It remains the reference value the others are all measured against, and the least useful number for deciding what to wear.

What the Calculator Does and Does Not Know

Every figure is computed from the numbers you type, in the browser, using standard published formulas. The page does not fetch a forecast, so it has no idea what the weather is actually doing where you are.

• No weather service is contacted; the temperature, humidity, wind and radiation values are entirely your inputs.
• The solar adjustment is applied on top of whichever method was chosen, including the wind-chill result, which assumes a shaded measurement in its published form.
• The methods are drawn from well-known published regressions, and the page names the one it used so you can trace the number.
• If any field is left empty, the page asks for a complete set rather than guessing a missing value.
• There is no location input and no time of day, so the sun's position is represented only by the radiation figure you supply.
• Nothing is uploaded or retained; the calculation is repeatable and the page stores no history.

Feels-Like Questions

Why do I get the Australian value when the weather is hot but dry?

Because the heat index requires the humidity to be at least 40 percent. On an 85 degree day at 30 percent humidity that condition fails, and since the temperature is above 50 the wind chill does not apply either, so the fallback that covers all ordinary conditions is used instead.

What does the solar figure do to the result?

It adds two hundredths of the radiation value, in watts per square metre, to the chosen temperature. At 300 the addition is 6 degrees and at 600 it is 12, so the sun is treated as a straightforward lift applied on top of whichever method was selected.

Does the page use a different formula for Celsius input?

No. A Celsius temperature is converted to Fahrenheit first and the same formulas are then applied. The result is converted back to Celsius for display when Celsius is the chosen unit, so the underlying calculation is equivalent either way.

Why is the wind chill not shown on a mild day?

Because the formula is only considered valid at or below 50 degrees Fahrenheit with wind of at least 3 miles per hour. Outside those bounds the page leaves it out entirely rather than printing a value the formula was never meant to produce, which is why the comparison block sometimes shows only one or two methods.

Can I use this to plan what to wear tomorrow?

Only if you already know tomorrow's temperature, humidity, wind and sunlight. The page calculates from what you enter and gathers no data of its own, so it is a way to interpret a forecast you have in hand rather than a way to obtain one.

Last verified: October 3, 2026

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Maintained by Huang Bin · Last updated October 3, 2026