Enter the maximum daily temperature, minimum daily temperature, and the coefficient that depends on the length of daylight hours into the calculator to determine the Huglin Index.

Huglin Index Formula

The following formula is used to calculate the Huglin Index. 

HI = ∑ ((Tmax + Tmin) / 2 - 10) * K

Variables:

  • HI is the Huglin Index
  • Tmax is the maximum daily temperature (°C)
  • Tmin is the minimum daily temperature (°C)
  • K is a coefficient that depends on the length of daylight hours

To calculate the Huglin Index, add the maximum daily temperature to the minimum daily temperature and divide by 2. Subtract 10 from the result. Multiply this by the coefficient that depends on the length of daylight hours. Sum these values over the period of interest (usually the growing season for a particular crop).

What is a Huglin Index?

The Huglin Index, also known as the Huglin Heliothermal Index, is a method used in viticulture to measure the suitability of a region for grape vine cultivation. It takes into account the daily mean temperature and daylight hours during the growing season to calculate a cumulative value. This value is then used to classify the region into one of several categories, ranging from cool to hot, which can help determine the types of grapes that can be successfully grown there.

How to Calculate Huglin Index?

The following steps outline how to calculate the Huglin Index:

  1. First, determine the maximum daily temperature (Tmax) in degrees Celsius (°C).
  2. Next, determine the minimum daily temperature (Tmin) in degrees Celsius (°C).
  3. Next, calculate the average temperature by adding Tmax and Tmin, dividing the sum by 2, and subtracting 10.
  4. Finally, multiply the average temperature by the coefficient (K) that depends on the length of daylight hours.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge:

Maximum daily temperature (Tmax) = 30°C

Minimum daily temperature (Tmin) = 15°C

Coefficient (K) = 0.5