Quote:
Originally Posted by Kassad
So I read that the dew point is the way to measure the 'comfort' level of an area. Then I also read that another way is to add dew point + temp. Greater than 130 and it starts to get uncomfortable. Greater than 150 and it gets gross.
So I have been feeding in cities to this weather web site and I see that Carmen, Mexico has the following information:
Elevation = 6600 feet
Temperature = 59 degrees F
Dew Point = 56 degrees
Humidity = 91 percent
This was done around 9:00am east coast time.
So using the above math, dew point+temp = 115 which would suggest it is really really comfortable, like San Diego comfortable. So given this can we disregard the 91 percent humidity and conclude that this climate is really comfortable?
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First off, you can't judge a climate based on one observation. That would be like saying my climate is a tropical paradise just because it was 83*F (28*C) yesterday.
As for dew point versus humidity, the dew point is an absolute measure of the amount of water vapor in the air; the dew point is the temperature at which condensation would occur, assuming water vapor level remained constant. The temperature cannot be below the dew point, just as the humidity can't be above 100%. The higher the dew point above a certain point (somewhere between 50 [10] and 75 [24] depending on the person; for me it's about 65 [18]), the more uncomfortable and humid it feels:
Below 55 (13): Comfortable 
55-64 (13-18): Noticeable but ignorable
65-69 (18-21): Getting muggy 
70-74 (21-23): Uncomfortable 
75-79 (24-26): Oppressive 
80 (27) or above: Unbearable 
The relative humidity (the percentage) is the ratio of how much water vapor there is in the air relevant to the maximum it can hold (i.e. 100% humidity). If the water vapor capacity of a mass of air is 10 kg and the actual amount in that mass of air is 6 kg, the relative humidity is 60%. This number is generally irrelevant to comfort levels.
The temperature is the measure of how warm or cold the air is, and it can be measured in Fahrenheit, Celsius, or Kelvin degrees. (Kelvin is merely Celsius plus 273.15.) You used Fahrenheit in your post, so I'll keep talking in terms of Fahrenheit degrees.
For most people, a neutral room temperature would be about 72*F (22*C), give or take a few. Below this temperature, a sensation of cool or cold will be present, and above this temperature, a sensation of warmth or heat will be present. Obviously the farther the temperature is from your comfort zone, and the worse-prepared you are for the temperature, the more uncomfortable you will be.
Frigid: Below 15 (-9)
Very Cold: 15-32 (-9 to 0)
Cold: 32-49 (0-9)
Cool: 50-65 (10-18)
Mild: 66-83 (19-28)
Warm: 84-94 (29-34)
Hot: 95-109 (35-43)
Sweltering: 110 (43) and higher
This is my personal temperature comfort scale; yours may vary. Mild is the near-neutral zone, where you are neutral, or at most slightly warm or cold. Cool and warm are also generally comfortable ranges, cold and hot are uncomfortable but tolerable, and frigid and sweltering are oppressively cold and hot respectively. Dew point, wind, and solar strength also have an impact on how warm or cold it feels; 60 (16) with strong wind, full overcast, and heavy rain would feel cooler than 60 with brilliant sunshine and calm wind.
In terms of heat-and-humidity discomfort, the higher the temperature is above your mild zone, and the higher the dew point is above your comfort zone (83 and 65 for me), the more uncomfortable it will be. 90 (32) with a dew point of 70 (21) is noticeably warm and humid, but not extremely oppressive or hazardous. 105 (41) with a dew point of 90 (32), on the other hand - yowza. 40 (4) with a dew point of 15 (-9) isn't any more comfortable than 72 (22) and 50 (10), unlike what your second formula said; 40 is just plain cold!
I hope I cleared up some stuff, and I'm sorry if this post was very long or confusing.
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