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A Discussion on Water Vapor (Moisture)


If the air temperature was 95 F with a dewpoint of 70, would the air's relative humidity be higher or lower than if the air temperature was 70 with a dewpoint of 55? Which air mass would feel more uncomfortable to you?


If the air temperature was 95 and the dewpoint temperature was 70, the relative humidity of this air mass would be 45 percent. The relative humidity in this case seems rather low, doesn't it, despite a hot air temperature and high dewpoint? Conversely, the relative humidity for the air mass with a temperature of 70 and a dewpoint of 55 would be about 60 percent. In other words, the relative humidity for this cooler air mass containing less moisture would actually be HIGHER than that for the hotter, more humid air mass. This shows how relative humidity can be very misleading and that one cannot consider relative humidity alone to determine how humid it feels outside. In this example, obviously the air mass with a relative humidity of 45 percent would feel more uncomfortable than the air with a relative humidity of 60 percent.

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