If you have the temperature and relative humidity, then you don’t need the dew point to find the heat index. However, you can find calculators for the heat index that just use the temperature and dew point. That’s because the three factors are interrelated.
The dew point is the temperature at which the air would need to be cooled, at constant pressure, so that the relative humidity would be 100%; the dew point can not be higher than the actual temperature. If the temperature were to cool below the dew point, then the water in the air in gas form (vapor) would condense into liquid, such as via rain or fog.
Warmer air can hold more moisture before it becomes saturated. A higher dew point means that there is more moisture in the air than there would be at a lower dew point. A dew point above 75F can feel oppressively muggy.
Relative humidity is the ratio of the amount of moisture present in the air relative to the amount that would be present if the air were completely saturated. It is dependent on dew point and temperature.
Relative humidity at 100% will feel less humid if the dew point temperature is 30F, for example, compared to, say, 60F.
So, it sounds like the weather report gave an extra statistic to help viewers to know the entire picture of how hot and muggy it was outside that day, although all of those stats are related.
If you have the temperature and relative humidity, then you don’t need the dew point to find the heat index. However, you can find calculators for the heat index that just use the temperature and dew point. That’s because the three factors are interrelated.
The dew point is the temperature at which the air would need to be cooled, at constant pressure, so that the relative humidity would be 100%; the dew point can not be higher than the actual temperature. If the temperature were to cool below the dew point, then the water in the air in gas form (vapor) would condense into liquid, such as via rain or fog.
Warmer air can hold more moisture before it becomes saturated. A higher dew point means that there is more moisture in the air than there would be at a lower dew point. A dew point above 75F can feel oppressively muggy.
Relative humidity is the ratio of the amount of moisture present in the air relative to the amount that would be present if the air were completely saturated. It is dependent on dew point and temperature.
Relative humidity at 100% will feel less humid if the dew point temperature is 30F, for example, compared to, say, 60F.
So, it sounds like the weather report gave an extra statistic to help viewers to know the entire picture of how hot and muggy it was outside that day, although all of those stats are related.