It’s Not the Heat, Nor the Humidity
It’s the dew point. That’s the meteorological measure that best predicts how tough your summer running is going to be.
Simply put, the dew point is the temperature at which water condenses. The closer the dew point is to the air temperature, the more saturated the air is and the less perspiration can evaporate and help the body cool itself, resulting in extra stress on the heart and lungs as the body attempts unsuccessfully to cool itself. Accordingly, the dew point provides a strong indicator of how you’ll feel running and a useful tool in predicting how much performance will be impacted.
DEW POINT (°F) :RUNNER’S PERCEPTION :HOW TO HANDLE
- 50-54 : Very comfortable : PR conditions
- 55-59 : Comfortable : Hard efforts likely not affected
- 60-64 : Uncomfortable for some people : Expect race times to be slower than in optimal conditions
- 65-69 : Uncomfortable for most people : Easy training runs might feel OK but difficult to race well or do hard efforts
- 70-74 : Very humid and uncomfortable : Expect pace to suffer greatly
- 75 or greater : Extremely oppressive : Skip it or dramatically alter goal
From Running Times Magazine : Training in the Heat
Dew point for my run tomorrow will be 68° (air temp 75°, humidity 84%). Suck factor of 7/10.