@ai6yr The study I continually cite is empirical research from Penn State, which suggests 87F wet bulb (roughly 31C) kills even young, healthy adults: https://www.psu.edu/news/research/story/humans-cant-endure-temperatures-and-humidities-high-previously-thought
@skyfaller Yikes, the entire East Coast on July 4th mid-day.
Jul 2, 2026, 9:06 PM@ai6yr and a big part of Europe, indoors, this time of the year.
[Edit: a friend of mine just asked me if he should just open the windows, 31C outside, 30C inside but with 68% humidity - he lives in a basement with small, shallow windows, no forced air exchange apart from a bathroom fan, we're in our country's capital, Lisbon -, I had to explain that outside the humidity is under 40% right now, just let the dry air enter and let the humid air out, it'll feel colder even if the temperatures get a little bit higher - for now.]
@skyfaller
@skyfaller@jawns.club @ai6yr@m.ai6yr.org luckily here in Las Vegas, it can get hot, but it’s almost never humid. 10% humidity is high humidity. And I live without air conditioning.
@skyfaller And the thing you almost never hear about is that the ability to tolerate temperatures varies from one body to another. Some people's systems are just different and they're the ones, regardless of age, who pass out when everybody else is doing fairly well. That random roll of the dice called genetics.
@skyfaller @ai6yr "researchers found that critical wet-bulb temperatures ranged from 25°C to 28°C in hot-dry environments and from 30°C to 31°C in warm-humid environments"
This doesn't make sense to me. I've been camping, hiking, biking in these temperatures without having a heat stroke. "25-28 in hot dry environments" 28 is not even hot?? That's a nice day at pretty much any humidity.
When I've heard 35 I'm like sure, that's dangerously hot. 28??
@ryanprior @skyfaller @ai6yr Wet bulb temperature is lower than the real air temperature unless there's 100% relative humidity. It is the lowest temperature achievable by evaporation.
For example: 35°C with 50% relative humidity is a wet bulb temp of 27.5°C
@grumpybozo @ryanprior @skyfaller @ai6yr
so, it's the lowest temperature sweating can make the air around you feel like?
@paul_ipv6 @ryanprior @skyfaller @ai6yr In principle, yes.
See elsethread for mention of wet bulb GLOBE temperature (bad name) which attempts to mix in the effects of radiative heating and imperfect evaporation into a metric that is supposed to represent how uncomfortable it really is.
The 1st toot pointed to wbGt forecasting by the National Weather Service. The research linked to by Nelson’s toot was about wbt, which is a directly measurable value.
@grumpybozo @paul_ipv6 @ryanprior @ai6yr you absolutely can directly measure Wet Bulb Globe Temperature, you just need special equipment. I have this relatively inexpensive device, although I can't say how accurate it truly is: https://sperdirect.com/products/wearable-wbgt-heat-stress-meter-with-tripod-mount
You can pay this shop extra to certify the accuracy of each device, and although that would make it significantly more expensive, I'm kicking myself for not doing it, because I'd like to trust my gear more, given life-threatening danger.
@skyfaller @paul_ipv6 @ryanprior @ai6yr Semantic difference. You can certainly get a device that will do all the needed measurements and calculations for you for WBGT, but it is doing multiple measurements: WBT (or dew point,) DBT, and "black globe bulb temperature." WBGT is defined as a value calculated from those 3 measured values.
WBT is directly measured by a thermometer with a wet wick on the bulb.
@grumpybozo @ryanprior @skyfaller @ai6yr Thank you for such a great way to explain this. I wonder if they should express it in a different way than degrees. Perhaps percentage? E.g., Today's wet bulb score is 98% [of being deadly for even young, healthy people]
@sbourne @grumpybozo @skyfaller @ai6yr wet bulb temperature doesn't strike me as a useful thing to report, now that I understand it a little better. It describes a specific measure that's useful in context, but seems to require a lot of interpretation before you can use it to make decisions about how to plan your day.
@sbourne @ryanprior @skyfaller @ai6yr It’s the base value from which all other measures of heat+humidity are derived. It’s used to calculate relative humidity, dew point, “Heat Index,” and the badly-named “wet bulb globe temperature,” each of which tries to express… something.
It is a non-obvious metric. It’s a bit difficult to express as a percentage because with different zero points for Celsius and Fahrenheit, the ratio of current temp to WBT would vary between the two & hard to convert.
@grumpybozo @ryanprior @skyfaller @ai6yr It's a hard communications problem. It's complicated, but important when it reaches life and death levels. I hope somebody more clever than I can figure out out!