Rising Heat index in Iran

As per a recent report, Iran’s coastal region has recorded a scorching heat index of 70 degrees Celsius (°C) in the coastal part of the country, a metric at which survival of life is not impossible. Also, the region recorded a heat index of 66.7 °C.

What is a Heat Index?

• Heat index, also known as apparent temperature, is a measure of how the temperature feels to humans.
• Relative humidity is an important factor that determines heat index, along with air temperature.

How Heat index is measured?

• Robert Steadman's Formula: In 1979, Dr. Robert Steadman, a professor at Colorado State University, developed a complex formula to calculate heat index.
  • This formula considers factors like temperature, humidity, wind speed, and barometric pressure to determine the apparent temperature, or what humans perceive as the temperature.
• Considerations for a "Typical Adult": Dr. Steadman's study was based on a "typical adult human of either sex, with a height of 1.7 metres and a weight of 67 kg."
  • This standardization allows for a consistent calculation of heat index applicable to a broad range of individuals.
• Inclusion of Dew Point: Dew point is a critical factor in heat index calculations.
  • It represents the temperature at which air can no longer hold all its moisture, causing condensation.
  • Steadman used a specific dew point value of 14°C in his calculations.
  • This factor is crucial in assessing the sultriness or discomfort associated with a particular temperature-humidity combination.
• Alternative Indices: While Dr. Steadman's formula is widely recognized, some countries, like Canada, have developed their own indices.
  • Canada uses Humidex, which considers temperature and dew point, but has its own specific formula for calculation.
  • This emphasizes the importance of tailoring heat index calculations to local climate conditions.

Why a specific heat index is important?

• Moisture Capacity and Apparent Temperature: Hot air has a greater capacity to hold moisture than cold air. When the temperature rises, the air's ability to hold moisture also increases.
  • This affects the apparent temperature or heat index, making humid air feel even hotter to humans.
  • This is why the heat index is a more useful metric than just the temperature alone.
• Effects of High Humidity on the Body: High humidity during heatwaves can lead to heat stress.
  • In these conditions, the body struggles to dissipate excess heat.
• Impact of Humidity: Conversely, in low humidity conditions, sweat can evaporate more efficiently, making the apparent temperature feel closer to the actual air temperature.
• Dangerous Heat Index Values: A heat index value of 67°C or above is extremely dangerous for both humans and animals with direct and prolonged exposure. At this level, heat-related illnesses become a serious risk.
• Categorization of Heat Levels

        Green: - Experimental heat Index less than 35 deg C

        Yellow: - Experimental heat Index in the range 36-45 deg C

        Orange: - Experimental heat Index in the range 46-55 deg C

        Red: - Experimental heat Index greater than 55 deg C

• Public Health: By understanding the Heat Index, individuals and communities can take proactive steps to protect public health during heatwaves.