I'm not sure I understand what that means exactly. If you're sitting in the shade and have enough water, how is 94f going to kill you? I've survived 110+.
Wet bulb is taking into account evaporative effects. You wrap a wet cloth around the thermometer to measure the temperature. This imitates human evaporative cooling, which is what your sweat is for. The point is that at high wet bulb, you can't cool yourself naturally in any way, can't expell heat into the environment, and will die.
Wet bulb temperatures are a combination of temperature and humidity, basically a rough measure of how much heat gets removed through optimal evaporation in given conditions.
Unfortunately the metric is both unclear on its face and a bit flawed in that a given wet bulb temperature can mean wildly different things depending on the actual temperature. The lowest wet bulb numbers that have been found to be extremely dangerous are basically a combination of extremely high heat with low or moderate humidity (IIRC those studies also entailed taking Americans used to AC and making them run on a treadmill in an extremely hot, dry room while hooked up to monitoring equipment), while the same wet bulb temperatures being caused by lower temperatures and high humidity are unpleasant but not life threatening unless there are extenuating circumstances (age, illness, certain medications, long covid, etc), and most of those extenuating circumstances already make lower, more normal temperatures dangerous already.
Basically, as long as the actual temperature is still below body temperature you still lose heat to the environment, you just lose a lot of efficiency through evaporation not working as well, it's when the temperature is above body temperature (and the higher it goes the worse it is) that it gets bad even when the wet bulb is still lower, because then you're not passively losing heat to the environment anymore (and in fact are gaining heat from the environment) and you need the efficiency gains of perspiration to survive.
This isn't the event horizon that it gets billed as, it's just further escalation of already deadly conditions that kill tons of people every year for class based reasons, part of the ongoing capitalist social murder of the working class. It means outdoor workers need more ability to stop work and cool off, or outdoor work needs to stop during the hottest part of the day altogether, and it means elderly people or people with other health problems need climate controlled shelter, but all of these things are already true, and they are materially stopped for classist and racist reasons.
That line is really important in this context because evaporation functionally doesn't happen at 100% humidity because the air is already saturated with water (I think technically evaporation still happens but only very little). If it's really hot but still sub 100% humidity, your sweat still functions, even if it really works best in dry heat. Past that, it stops helping and you're just soaked in hot sweat that accumulates.
You won't just drop dead, but barring some other actually effective means of cooling yourself, you will overheat and die in those conditions.
It means it's so humid that sweat no longer cools you down. Your internal temperature just keeps increasing until you die. That 110 was probably pretty dry.
so it is temperatures that can kill the sick and frail
this is misinformation!
Humidity worsens the effects of heat because humans cool their bodies by sweating; water expelled through the skin removes excess body heat, and when it evaporates, it carries that heat away. The process works nicely in deserts, but less well in humid regions, where the air is already too laden with moisture to take on much more. Evaporation of sweat slows. In the most extreme instances, it could stop. In that case, unless one can retreat to an air-conditioned room, the body's core heats beyond its narrow survivable range, and organs begin to fail. Even a strong, physically fit person resting in the shade with no clothes and unlimited access to drinking water would die within hours.
Meteorologists measure the heat/humidity effect on the so-called "wet bulb" Centigrade scale; in the United States, these readings are often translated into "heat index" or "real-feel" Fahrenheit readings. Prior studies suggest that even the strongest, best-adapted people cannot carry out normal outdoor activities when the wet bulb hits 32 C, equivalent to a heat index of 132 F. Most others would crumble well before that. A reading of 35—the peak briefly reached in the Persian Gulf cities—is considered the theoretical survivability limit. That translates roughly to a heat index of 160 F. (The heat index actually ends at 127 F, so these readings are literally off the charts.) "It's hard to exaggerate the effects of anything that gets into the 30s," said Raymond.
You cannot sweat at 100% humidity. (Or rather, sweat doesn't evaporate, meaning it can't cool you.)
A wet-bulb temperature of 94 F is fatal, even for the most strong and adapted. Remember that you are warm-blooded and need to shed heat at all times in order to not cook yourself to death.
I'm not sure I understand what that means exactly. If you're sitting in the shade and have enough water, how is 94f going to kill you? I've survived 110+.
Wet bulb is taking into account evaporative effects. You wrap a wet cloth around the thermometer to measure the temperature. This imitates human evaporative cooling, which is what your sweat is for. The point is that at high wet bulb, you can't cool yourself naturally in any way, can't expell heat into the environment, and will die.
Wet bulb temperatures are a combination of temperature and humidity, basically a rough measure of how much heat gets removed through optimal evaporation in given conditions.
Unfortunately the metric is both unclear on its face and a bit flawed in that a given wet bulb temperature can mean wildly different things depending on the actual temperature. The lowest wet bulb numbers that have been found to be extremely dangerous are basically a combination of extremely high heat with low or moderate humidity (IIRC those studies also entailed taking Americans used to AC and making them run on a treadmill in an extremely hot, dry room while hooked up to monitoring equipment), while the same wet bulb temperatures being caused by lower temperatures and high humidity are unpleasant but not life threatening unless there are extenuating circumstances (age, illness, certain medications, long covid, etc), and most of those extenuating circumstances already make lower, more normal temperatures dangerous already.
Basically, as long as the actual temperature is still below body temperature you still lose heat to the environment, you just lose a lot of efficiency through evaporation not working as well, it's when the temperature is above body temperature (and the higher it goes the worse it is) that it gets bad even when the wet bulb is still lower, because then you're not passively losing heat to the environment anymore (and in fact are gaining heat from the environment) and you need the efficiency gains of perspiration to survive.
This isn't the event horizon that it gets billed as, it's just further escalation of already deadly conditions that kill tons of people every year for class based reasons, part of the ongoing capitalist social murder of the working class. It means outdoor workers need more ability to stop work and cool off, or outdoor work needs to stop during the hottest part of the day altogether, and it means elderly people or people with other health problems need climate controlled shelter, but all of these things are already true, and they are materially stopped for classist and racist reasons.
not at 100% humidity you havent
Close to it, but sure, not exactly 100%.
That line is really important in this context because evaporation functionally doesn't happen at 100% humidity because the air is already saturated with water (I think technically evaporation still happens but only very little). If it's really hot but still sub 100% humidity, your sweat still functions, even if it really works best in dry heat. Past that, it stops helping and you're just soaked in hot sweat that accumulates.
You won't just drop dead, but barring some other actually effective means of cooling yourself, you will overheat and die in those conditions.
It means it's so humid that sweat no longer cools you down. Your internal temperature just keeps increasing until you die. That 110 was probably pretty dry.
Nope, not dry at all. But yeah, not so humid you can't sweat.
Keep in mind I'm in that black zone on the map.
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this is misinformation!
https://phys.org/news/2020-05-potentially-fatal-combinations-humidity-emerging.html
You cannot sweat at 100% humidity. (Or rather, sweat doesn't evaporate, meaning it can't cool you.)
A wet-bulb temperature of 94 F is fatal, even for the most strong and adapted. Remember that you are warm-blooded and need to shed heat at all times in order to not cook yourself to death.
scientists got some wet bulbs if you know what I mean
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Right, ok, yeah that makes sense. Definitely don't want your 98 year old grandmother to work in 110+