Humidity and dew point

Feeling uncomfortably warm…

Runner: Must be the humidity.

Meteorologist: Partly, yes.

Runner: But it’s the moisture in the atmosphere, isn’t it?

Meteorologist: Dew point. At a cooler dew point like 6 degrees Celsius you feel comfortable, but if the dew point rises to 18 or 20 degrees C you feel sweaty and uncomfortable.

Runner: I’ve seen dew point on the weather forecast.

Meteorologist: Dew point. The atmospheric temperature when water droplets condense and form dew. There’s a formula which takes account of pressure and humidity. Dew point is a better measure to predict what to wear.

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Voice-over

The actual formula is Td = T - ((100 - RH)/5.) where Td is dew point temperature (in degrees Celsius), T is observed temperature (in degrees Celsius), and RH is relative humidity (in percent). This table sums up how dew point relates to how you feel.