This index adds a little more information to the heat index by adding wind.
(The heat index assumes the wind is calm.) While we usually think of wind as cooling,
wind will make you feel even hotter if it's warm enough (over 34°C).
In the winter the THW index almost “perfectly” follows the wind chill and in the summer
quite to very well the heat index
In general, weather templates display the THW index next to the temperature. The information
is shown as the Apparent (or 'Feels Like') Temperature. Depending on the season or or the
measured temperature (f.i. below 10°C), wind chill is displayed instead.
This index is less often mentioned. Here the S stands for “sun” (the others are equal
to the THW index) the effect of the sun is indeed clearly recognizable. The positive effect
of the sunshine is visible in the winter when the weather is freezing cold and in the summer
when the weather is oppressively warm, the negative effect is visible (higher index value in
both cases). When there is no sunshine, the development of the TSHW index is always slightly
lower than the THW index. Incidentally, it is not the sunshine, but the global radiation that
is included as a parameter in the TSHW index.