What is “wet bulb temperature” and why does it matter?
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A lot of these answers relate directly to what it means for humans. While this is important, there is a slightly different explanation, so here is what means to those of in the Wildland fire community:
We have a tool called a sling psychrometer. It has two thermometers on it. One is the dry bulb, you hang it somewhere (preferably in the shade) and wait for it to stop moving. That’s the ambient air temperature. The second thermometer is the wet bulb. It has a small cotton wick on the bulb. We dip that in distilled water. The whole thing is on a little chain so you can spin it. The air movement dries the wet bulbs wick and the temp drops. When it stops dropping, that’s your wet bulb temperature.
We then have charts, based on elevation, that allow us to cross reference the wet and dry bulb to get the relative humidity (%) and the dew point (°). RH is very important for determining how a fire is going to behave. We track all of this, and more, consistently on a wildfire and the trends/observations let us make more informed tactical decisions on how to fight the fire.
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