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Why 80 degrees "feels like" 95 degrees (and why this is stupid).

Wed 28 Jul, 2021 08:21 pm
We have all seen people on the news tell us what the temperature "feels like". "Feels like" temperatures are always more extreme (hot temperatures are made hotter, and cold temperatures colder). This is why the news likes them.

But how does telling you what the temperature "feels like" this make sense?

You know what 80 degrees feels like (or 27 degrees if you are not from the US). In truth if you estimate the actual temperature on the thermometer with in 2 or 3 degress (that's 1 ior 2 degrees for those outside of the US).

There is some science behind the "feels like" temperature. The scientific name for this is "wet bulb" temperature... and it is actually a function of both temperature and humidity. And it corresponds to the ability to use evaporative cooling to cool down (as the body does).

However the assumption here is that the your mind bases its estimation on temperature on zero humidity. Of course, this is ridiculous. None of us have any experience with a zero humidity environment.

So yes, if you are experiencing higher humidity than you are used to, you are going to be more miserable at a lower temperature. Sure. But to then compare it to the actual temperature is ridiculous. This is really a comparison of apples and oranges. The temperature (i.e. dry bulb temperature) measures one thing. The web-bulb temperature measures something completely different.

What something "feels like" is a mental state... you don't calculate it, you simply tell people how you feel. If the math disagrees about how you feel, the math is wrong. That being said, I find the "dew-point" another function of temperature and humidity to be more predictive of how miserable I am. But that is just my experience.

Since the dew point will almost always be lower than the high temperature you are experiencing, it is not nearly as sexy.
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oralloy

1
Thu 29 Jul, 2021 01:48 am
maxdancona wrote:
That being said, I find the "dew-point" another function of temperature and humidity to be more predictive of how miserable I am. But that is just my experience.

It is my experience as well.

A dewpoint of 50 degrees (or lower) is very comfortable weather.

A dewpoint of 60 degrees is noticeably humid, but it is not bad enough to be uncomfortable.

A dewpoint of 70 degrees (or higher) is intolerably humid.

Fahrenheit of course.

And obviously there are extremes where this breaks down. A temperature of 150 degrees would be uncomfortable (and probably lethal) even with a very low dewpoint.

Low dewpoints aren't everything though. Wildfires really like high temperatures combined with low dewpoints.
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coluber2001

1
Thu 29 Jul, 2021 08:41 am
It's the humidity, but it's also the breeze. The heat index used by weatherman to tell you how it feels does not taking account the movement of air.
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Walter Hinteler

1
Thu 29 Jul, 2021 09:10 am
Methods for the human-biometeorological assessment of climate and air hygiene are used since a couple of decades.
This was already done on an experimental basis in the 70's of the last century: for couple of days I had to collect weather data instead of the meteorologists on a damaged weather ship in the North Atlantic. (Didn't really know before what "wind chill" was.)

But I do think (and that's what I was told already back then) that meteorologists have no real use whatsoever for wind chill, a scientific measure of diddly and squat.
maxdancona

0
Thu 29 Jul, 2021 09:54 am
@Walter Hinteler,
Just to be clear, I have nothing against "human-biometeorological assessments".

The problem is when these metrics are compared to or confused with temperature. They aren't temperature.

It gets ridiculous when they say some human-biometerological metrie 'feels like a temperature".

There are no realistic conditions where 80 degrees will ever "feel like" 80 degrees. That makes the whole ideas silly.
Walter Hinteler

0
Thu 29 Jul, 2021 10:07 am
@maxdancona,
At least there are some, who think a bit differently.
The quote below is from the abstract of the report Review of Biometeorology of Heatwaves and Warm
Extremes in Europe

Quote:
The indices that take into account human energy balance along with weather conditions should be used to examine the impacts of extreme heatwaves on human health and should be used as a basis for the determination of acclimatization to high-heat-stress conditions
maxdancona

0
Thu 29 Jul, 2021 10:16 am
@Walter Hinteler,
I am not quite sure what your point is, Walter.

I am saying that these metrics should not be compared to temperature. You are saying these metrics are useful. It doesn't seem we are in disagreement.

Do you see the issue with people saying something "feels like" a temperature?
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Walter Hinteler

1
Thu 29 Jul, 2021 10:16 am
@Walter Hinteler,
Just adding that centrifugal thermometers and spin hygrometers were (are?) used to get the most exact data - kind of using the wind chill.
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hightor

1
Thu 29 Jul, 2021 11:19 am
I've often said the same thing about "wind chill" temperatures that they regularly trot out in the winter. It is helpful for people who don't pay attention to weather conditions. But don't mistake maxdancona's intention here. He just wants to rebut the point raised by Umair Haque which I posted HERE. Apparently he's offended that anyone would suggest that people are vulnerable to a combination of extreme heat and humidity.

NOAA wrote:
Sweating alone does nothing to cool the body unless the water evaporates. Around a wet-bulb temperature of 95°F (35°C), human’s survivability limit, evaporation of sweat is no longer enough for our bodies to regulate their internal temperature. But serious impacts occur at values as low as 79°F (26°C).

“When wet-bulb temperatures are extremely high, there is so much moisture in the air that sweating becomes ineffective at removing the body’s excess heat, like what happens in a steam room,” said Colin Raymond, the study’s lead author who conducted work at Columbia University and is now a postdoctoral scientist at NASA’s Jet Propulsion Laboratory. “At some point, perhaps after six or more hours, this will lead to organ failure and death in the absence of access to artificial cooling.”

maxdancona

0
Thu 29 Jul, 2021 11:34 am
@hightor,
Geez Hightor! There is a reason I started a new thread rather than reponding to your apocalyptic prophet of doom.

This is a different topic.
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engineer

2
Thu 29 Jul, 2021 11:49 am
@hightor,
The problem is the reference point. I grew up in New Orleans and in the summer, it was routinely 90+ degrees, 50+% humidity. If someone said it's 94 degrees, 50% humidity, feels like 103 and I stepped outside, I would have said, "no, feels like 94, this is always what 94 feels like." I have no reference point for what 103 degrees, zero humidity (or whatever the baseline is) feels like. The "feels like" temperature is really not valid unless it describes something people can relate to and it should go both higher and lower than actual. Rather than a valid observation it feels like a PR stunt. HEAT INDEX! CHILL FACTOR! No one ever says, "it's hot but dry today, feels pretty good out there but carry your water bottle!" That is not to say that biological stress is not a function of air temperature and humidity, just that the way it is used is more show than meaningful metric to help people. As for Umair Haque, I see where he is going but as a kid, I played for hours weather that he says would kill me. While I'm dramatically more careful now than I was as a kid, I still occasionally play tennis for over an hour in 90-95 degrees and high humidity and I'm chugging water hard, but no one is dying. Hard court tennis in the summer is often over 100. People are working all over the South in conditions that this chart says would kill people. I don't think his hypothesis matches the observations.

2
Thu 29 Jul, 2021 01:07 pm
@maxdancona,
Quote:
But how does telling you what the temperature "feels like" this make sense?

Because then you know how to prepare. I think the best example is the extreme cold - so say the actual degrees is 25F with wind chill so the real feel is now below zero - you know you really need to bundle up and it could be dangerous if you have skin exposed even a short period of time.

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hightor

1
Thu 29 Jul, 2021 01:19 pm
@engineer,
Quote:
I don't think his hypothesis matches the observations.

It's not "his hypothesis", he's simply reporting what others have said, like NOAA.
Quote:
I still occasionally play tennis for over an hour in 90-95 degrees and high humidity and I'm chugging water hard, but no one is dying.

Colin Raymond wrote:
“At some point, perhaps after six or more hours, this will lead to organ failure and death in the absence of access to artificial cooling.”

As I said, I've always taken the THI and the wind chill numbers with a degree of skepticism but they can be useful for people who don't have much experience or simply hear 90º and think it'll be fine and don't pay attention to the humidity. No one know what 103º "feels like" but if it's accompanied with a warning and a high THI it's hoped that the public will pay a little more. attention.

As was pointed out:

Because then you know how to prepare.
0 Replies

1
Thu 29 Jul, 2021 01:22 pm
@engineer,
This makes sense here - but I think if you hear from your local weather you sort understand what with "wind chill" or with "humidity" feels like in the concept of where you live day to day.
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Walter Hinteler

1
Thu 29 Jul, 2021 01:38 pm
@engineer,
engineer wrote:
The "feels like" temperature is really not valid unless it describes something people can relate to and it should go both higher and lower than actual. Rather than a valid observation it feels like a PR stunt
It actually is shown higher AND lower since the calculation is taking into account the expected air temperature, relative humidity and the strength of the wind at around 1.8 metres combined with the understanding of how heat is lost from the human body during cold, warm/hot and windy days.

Wikipedia has some background informations about wind chill -I'd used a wind chill calculator similar to the one shown in that article, but had to use a formula additionally.
maxdancona

0
Thu 29 Jul, 2021 02:15 pm
@Walter Hinteler,
Here is an experiment anyone can do.

1. Step outside, and estimate what the temperature is just by feel.

2. Then compare it to the official answer.

My hypothesis is that any time the temperature is above 75F, your estimate of the temperature by feel will be very close to the actual temperature. This number will almost always be significantly lower than the "feels like" temperature.
hightor

1
Thu 29 Jul, 2021 02:28 pm
@maxdancona,
Quote:
This number will almost always be significantly lower than the "feels like" temperature.

That's because people learn to associate the temperature with degrees. But you take a person from a warm climate and put them in northern New England and they'll often guess that it's cooler than the dry temperature. And vice versa. What if instead of "feels like" they said "acts as" or something to indicate the human body's ability to cool itself? It's harder to feel cool at 90º with a fan blowing on you if the humidity is high. I believe that's the point of the whole thing.
maxdancona

0
Thu 29 Jul, 2021 02:56 pm
@hightor,
Think about what you are saying, Hightor.

We are talking about what a temperature 'feels like". You seem to be suggesting that people are wrong about what a temperature feels like to them.

Of course people make associations based on their experience. That's part of the point. If a person reports what the temperature feels like to them, that is the correct answer. If a calculation comes up with a different answer for how they feel, that calculation is wrong by definition.

Math can do lots of cool things. Telling human beings how they feel isnt one of them.

2
Thu 29 Jul, 2021 03:17 pm
@maxdancona,
This is not what they are trying to do - make the feels like personal to each person, but to explain how to prepare again. Pretty much any reasonably intelligent person realize when they say "feels like" temperature - the person realizes that although the temperature may be 95 degrees due to the humidity it will feel significantly hotter. This helps people to say prepare their child with extra water at camp; maybe the camp to have more water sports; rather than running activities, etc. Or if it is cloudy and windy that 95 degrees may feel like 85 so again you will change your activities, your clothing, what you bring with you.

It is not supposed to be an exact science nor to explain how each individual person is going to feel - but overall how much more oppressive, bitter cold, or actually not as bad as it seems with the temperature. I think most reasonable people understand this. Real feel is supposed to give you better indication of how the temperature will really impact you so it is a better indicator of preparing than just the actual temperature itself.

Not to mention that providing actual temperatures in a weather report - is a prediction any way.
maxdancona

1
Thu 29 Jul, 2021 04:03 pm