Tuesday, November 16, 2010

Temperatures are Stupid

Is it just me, or does it seem like a sunny 25F day with snow on the ground and light winds can seem warmer than a cloudy, windy 55F day?  I've always believed that the temperature itself tells very little about what it actually feels like outside.  Let's start out with summer.  Growing up in Alabama, when the temperature got to 90F, there was a huge difference between a 72F dewpoint and a 68F dewpoint.  Playing golf all summer, on the 90/68 days I'd hardly sweat, but on the 90/72 I'd be dripping.  Cloudy, breezy days in the summer always felt way better too, all other things being equal.

However, once the temperature gets below about 60F, high humidities have a different role: they make it feel colder.  This gets extremely noticeable for temperatures near or just below freezing.  This may sound crazy, but I perceive winters up here in Alaska to only be a touch cooler than where I grew up in Alabama.  This is because in Alabama it was often quite humid when it was cold.  Plus, there's just something about snow on the ground (in Alaska, not Alabama) that makes you feel warmer than if there isn't snow.  Perhaps part of my perception of Alabama as cold is due to the fact that for some odd reason I loved wearing shorts in the winter, but I digress.

Wind is obviously another factor in how it really feels.  Obviously, there's a little thing called wind chill.  However, I've always thought that it's a bit overrated.  Let me explain way. 
  1. If you are properly dressed when it's really cold out, you don't have any exposed skin, thus the wind matters little.
  2. You can usually turn away from the wind, protecting yourself at least somewhat.   
  3. 33F is still 33F no matter the wind.  You can't get frostbite at 33F even though the supposed wind chill may be well below freezing.  Well, perhaps you could get a little frostbite if the air is really dry and your skin is wet with evaporative cooling going on, but generally speaking you need temps below freezing to get frostbite.  Of course, hypothermia can occur at much warmer temperatures.
  4. The wind you experience when outside is rarely the wind observed at an official measurement station, at least not for sustained periods.  Wind is measured is a big open field usually at an airport at 33 ft above the ground.  Not exactly representative for what you're experiencing.  An important exception is if you are on a ridgetop.


  1. Years ago in the middle of winter after a few windy days, I was standing outside with a friend around 10 PM. The temp was 25 degree with no wind and I did NOT feel cold in just a shirt.

  2. I'm outdoors for prolonged periods three or four days a week, and the sun (the radiant energy part) seems to make the biggest difference. If it is sunny and in the 20s, I can run in shorts and short sleeves and be comfortable. But a damp, cloudy, windy 48 can be really chilly. When I am trying to decide what to wear, I pay the most attention to sky cover and wind. Surroundings can also make a difference. I'm guessing the effect you mention with snow on the ground is partly because of reflected radiant energy. I don't know exactly what causes it, but I have also observed feeling warmer when snow is on the ground. Anyhow, I totally agree that air temperatures play only a small part in our perception of hot and cold.