We climbers love Fall. The tourists have left and the leaves are changing to gold and red. Pumpkin pie is considered an acceptable meal. Any meal. Most of all, the air is cool and dry, thus perfect for redpointing. Autumn is so good for climbing that Todd Skinner used to fantasize about making a film where a group of climbers traveled around the world to find the perfect conditions for climbing... he called it "Endless October."
But there is some pain in the ass that comes with Fall, too. For one thing, candy-corn becomes so common at the grocery store that it ends up the default vegetable at our house. This would be fine, but apparently it's sorta bad for your teeth. October days are also much shorter than summer days, being comparable to February in hours of daylight. Finally, Fall days require the most wardrobe changes at the crag as the variations in temperature can be extreme.
Temperature, as described by Lutgens Tarbuck in his meteorology standard The Atmosphere, is defined as "how warm or cold something is with respect to some standard measure." Yeah, we knew that, Lutgens. Mr. Tarbuck also describes temperature as a "measure of the average kinetic energy of the atoms or molecules in a substance." We didn't know that, and honestly still don't. I describe temperature in two diurnal standards; how hot it feels in the summer, and how cold it feels in the winter. "It's hotter than my wife in fishnet," and "It's colder than a witches thorax" being my standards.
In space there is no atmosphere to hold onto the heating of the suns rays. If the Russians managed to give you a ride up (thanks Congress) to the space station, and you took Laika for a walk, the incredible view might bring out the temptation to do a little tanning. Slipping off your space suit, you would feel a pretty extreme difference between shade and light. While looking toward the sun, your torso and face would be heating up well over 200 degrees Fahrenheit. Meanwhile, your hiny would be a crisp -150 F. Granted, this would not be near as much of a bother as the nitrogen boiling in your blood due to the complete lack of atmospheric pressure, but it does give a vivid example of the ability of the atmosphere to hold temperature.
On the summer solstice, June 21, the sun reaches it's highest point in the North American sky. That is the day the northern hemisphere is bathed in the most solar radiation. One would naturally think that on that day we should see our hottest temperature of the year. In contrast, the shortest day of the year, the winter solstice just before Christmas, when it's dark at like 5:30 in the afternoon, should be the day we see the coldest temperatures. But we don't. We never have. This is because there is a delay in how the atmosphere heats up and how it holds heat. The hottest days of the year are in late July and early August, and the coldest temperatures are usually a month after the winter solstice. It simply takes a while for the atmosphere to heat up, and also some time to cool down.
One of the things that makes Fall so nice is that the delay is still keeping it warmer than winter, but the westerly winds in the upper atmosphere have kicked in and moved the summer monsoonal pattern south, giving us a warm but dry month. Again, a warm but dry month with pumpkin pie.
The lack of moisture also has a lot to do with temperature. Lutgens describes humidity as "the amount of water vapor in the air." Because of certain traits of water, humid air holds on to heat better than dry air. We see this on damp summer nights, when hours after the sun has set it is still hot. We also see it on winter afternoons, where the air temperature in the shade is 20 degrees, but it's 50 on the sun baked slabs beneath Addiction. On a typical dry day in October, or like last Sunday, the dry atmosphere simply doesn't hold onto the heat when the suns direct rays are not shining on it. This makes for what feels like a hot day with the sun on your face, but cold crisp, shady pockets on the wall.
Last Sunday we found ourselves putting on shorts and going topless when the sun was shining, but wearing down jackets and a hat when belaying in the shade. One person commented how it was too hot to rock climb, and another, 30 feet away and in the shade, dropped onto the rope because her hands were numb from the cold pockets. This extreme variation is simply because despite the intensity of the sun, the atmosphere is holding little heat. Enjoy it. Soon enough I will be explaining Gulf of Alaska cyclones, how the wind affects the heating process along Sinks Main Wall, and of course lamenting a lack of pumpkin pie.