The weather this week has been brutal. The last hike I did in the upper 80s left me heat-stressed despite drinking lots of water. I stop exerting any effort at all in the 90s. In the 100s all I begin to estivate.
Every summer a big high pressure system sets up over the Great Basin Desert. That’s Nevada and Utah. The air heats up. Hot air expands producing high pressure. The Basin is at about 4-5,000 feet of elevation. Air flows out in a clockwise fashion into the surrounding areas. The surrounding areas in the south are the Mojave Desert which is mostly at 2-3,000 ft. The incoming air gets compressed heating it. Death Valley at 250+ ft. below sea level is the lowest point in the Mojave and because of that experiences the most compression. Ostensibly the hottest location in the world.
The Mojave is already insanely hot. Then this even hotter air comes blasting in. It doesn’t stop at the mountains north of LA. The hot air climbs and is cooled, squeezing any possible hint of moisture out. It then pours out of those mountains down into the low elevation valleys that are the Greater Los Angeles Area, picking up great speed, recompressing, and heating even more. (Known in meteorology as katabatic winds.) Relative humidity plunges into the teens and single digits. These are the famed Santa Anna winds.
The low humidity fails to hold in any heat at night, often resulting on 40 degree temperature swings.
Not the Satan winds, tho they seem hot as hell.. Not the Santa Anita winds, tho Santa Anita does feel them. Not the Santana winds, though I’m sure Carlos is extremely familiar with them. I hear newscasters brutally mangle the name of these winds all the time. These fires turn tiny sparks into raging infernos. They suck the water out of your lawns and gardens, contributing to the already extreme drought.
But… we still love LA. 🙂
Triple-digit weather combined with direct sun and physical effort can kill you very quickly. You can’t sweat fast enough to cool off and you can’t carry enough liquids to keep up with the sweating.
The best way to dress in the sun for super hot and dry weather is layers of loose cloth. It provides shade to the skin yet allows air to circulate and traps some moisture next to our body. The the body works very hard to keep the skin surface close to 100% humidity thru insensible perspiration at all times. It is a very large source of water loss.
Skin in direct sun can climb to 104F (40C) if you are healthy and more if you are dehydrated. A person’s standing body is hit by 500 watts of solar heat energy continually, depending on body size. A sun bather perpendicular to the sun can receive double that. This is in addition to the heat from the air.
In super hot and moist weather you still want shade but you don’t want clothing because water doesn’t evaporate well in high humidity, You want to give the water every chance possible to evaporate. We lost our fur because it was advantageous to our hunting style – “persistence hunting.” Furry people overheated when chasing down game.
In the military, they taught us to always check our urine in hot weather. Needs to be clear to light. Medium to dark yellow is a sign you need to drink more. If you suffered from any dehydration related illness, you written up and punished for to obey standing orders.
Someone who is acclimated will last a lot longer. Unless you’ve been an outdoor laborer for a while, I guarantee you are not acclimated. Most of the urban population does not ever acclimate, even if they are in good cardiovascular condition. (I know I don’t.) Too much air conditioning in our lives. Most of us have to make an effort to drink enough in hot weather because the thirst reflex doesn’t kick in properly. People simply forget to drink and next thing they know, they get head aches and feel faint. Welcome to hyperthermia. So be safe!
If you are vulnerable to heat issues – the very old, the very young, the ill, – and the AC goes down, be extra sure to drink more water than you want. Stay inside and close the curtain on the sides of your exposed to the sun. On the other side, open the window and hang wet towels in front of it. Take cold baths. Give cool baths if you are a caregiver. Get wet and let nature cool you off. Keeping your head cool is the most important thing of all. An overheated brain is what kills you.
Please don’t be this person!