Heat Index Calculator
Find the 'feels like' temperature from air temperature and humidity — Pakistan summer heat
Frequently Asked Questions
Heat index — the "feels like" temperature — combines air temperature and relative humidity into a single figure that better represents how hot conditions actually feel to the human body than air temperature alone, which matters directly during Pakistan's summer heat, when high humidity in some regions makes actual temperatures feel considerably hotter.
Why humidity changes how heat actually feels
The human body cools itself primarily through sweat evaporation — as sweat evaporates from skin, it carries away heat. High humidity slows this evaporation process, since humid air is already closer to its moisture-holding capacity and absorbs sweat moisture more slowly than dry air does — which means the body's primary cooling mechanism becomes less effective in humid conditions, making a given air temperature feel meaningfully hotter than the same temperature would feel in dry air. Heat index quantifies this combined effect into a single "feels like" number, which is why two locations or days with identical air temperature but different humidity levels can have genuinely different heat index values and different actual heat stress on the body.
A worked example
The identical air temperature reading in a low-humidity location versus a high-humidity one produces different heat index values — the high-humidity location's heat index runs higher, reflecting that the body's evaporative cooling is less effective there, even though the thermometer reading itself is identical in both places.
How this connects to your other weather calculations
For a related but distinct calculation specifically about the temperature at which air becomes saturated (rather than how hot conditions feel), the Dew Point Calculator covers that companion concept — dew point and heat index both derive from the same underlying temperature-humidity relationship but answer different practical questions.
Common mistakes
Judging expected heat stress purely from the air temperature reading, without factoring in humidity, is a common way people underestimate real heat risk during Pakistan's humid summer months — two days with the same thermometer reading can have meaningfully different actual heat stress on the body, and heat index (not raw temperature alone) is the more reliable figure for judging genuine heat risk.