实用工具

Heat Index Calculator

🌡️酷热指数计算器

Temperature (°C)

Best for T > 27°C / 80°F

相对湿度 (%)

40–100%

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Detailed Guide Coming Soon

We're working on a comprehensive educational guide for the Heat Index Calculator in your language. The content below is shown in English.

是什么 Heat Index Calculator?

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The heat index (also called apparent temperature or feels-like temperature in summer) estimates how hot it actually feels based on air temperature and relative humidity. High humidity prevents sweat from evaporating effectively, reducing the body's ability to cool itself. The Rothfusz (1990) regression equation used by NOAA and the NWS is the most widely accepted formula.

Calkulon makes complex calculations simple — built for students and everyday problem-solvers.

公式

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f(x)HI = −42.379 + 2.04901523T + 10.14333127R − 0.22475541TR

变量说明

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符号	名称	单位	描述
HI	−42	—	−42

如何 Heat Index Calculator

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1Based on Rothfusz (1990) regression of physiological studies
2HI = −42.379 + 2.04901523T + 10.14333127R − 0.22475541TR ...
3T = air temperature (°F), R = relative humidity (%)
4Applies when T ≥ 80°F (27°C) and RH ≥ 40%
5Accuracy: ±1.3°F under typical conditions

例题解析

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示例 1

已知:35°C, 60% humidity

结果:Heat index ≈ 42°C — feels significantly hotter

Health risk threshold

示例 2

已知:40°C, 80% humidity

结果:Heat index ≈ 60°C — extreme danger

Can be fatal without cooling

实际应用

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Tracking personal health and fitness goals

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Guidance for healthcare conversations with your doctor

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Monitoring progress during a weight management programme

Heat Index Categories (NOAA)

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Feels-Like Temperature	Category	Health Effects
27–32°C (80–90°F)	Caution	Fatigue with prolonged exposure
33–39°C (91–103°F)	Extreme Caution	Possible heat cramps/exhaustion
40–51°C (104–124°F)	Danger	Heat cramps/exhaustion likely; heat stroke possible
> 52°C (125°F)	Extreme Danger	Heat stroke highly likely

常见问题

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What is Heat Index Calc?

How accurate is the Heat Index Calc calculator?

The calculator uses the standard published formula for heat index calc. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Heat Index Calc calculator use?

This calculator works with inches, Celsius, Fahrenheit, percentages. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Heat Index Calc calculator use?

The core formula is: HI = −42.379 + 2.04901523T + 10.14333127R − 0.22475541TR . Each step in the calculation is shown so you can verify the result manually.

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专业提示

Heat index assumes shaded conditions. Direct sunlight can add an additional 8–15°C to the apparent temperature. Drink water before you feel thirsty — thirst indicates you are already mildly dehydrated.

参考资料

Formula-verified for precision

Reviewed October 2026

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