You know those days when you walk outside, prepared to run, and you start sweating immediately? Don’t blame the temperature, it is all in the dew point. Now I’d never heard of this measurement until speed work one miserable day; I started kvetching almost immediately when I entered the track and coach explained that it was the dew point, not the humidity, that was killing me. According to coach (and science) the dew point is the temperature where water vapor will condense into water. To put it a bit more plainly, the higher the dew point, the harder it is for your sweat to evaporate. Sounds pleasant, huh?
Now before I go out for a run, I check the temperature and dew point. It helps to prepare mentally. If the dew point is above 65° then I know not to push myself too hard. The last thing anyone needs is to faint or become horribly dehydrated in this weather. If you notice that the dew point will be lower later in the day, consider changing your routine for the day. Remember to have water and a towel (or absorbent top) easily accessible if you are heading out in less than ideal conditions!
Check out this quick article (courtesy of coach) that gives a slight break down of the different ways to handle the varying dew points – Dew Point Information If you want a more detailed explanation, well then go to Wikipedia (obviously).
Is this a measurement you’ve ever heard of? Do you take dew point into consideration before going outdoors?