'Feels' hotter than it is?

[ColinJ]

I was just looking at the Met Office local forecast ...

I can understand how windchill can make standing outdoors feel colder than the actual air temperature, but I can't get my head round how it can feel hotter than it is!

Is that just a Met Office glitch or is there a sensible explanation?

 

[gavgav]

It's a interesting one!! Maybe to do with Humidity? But even so I'm not sure it can feel hotter than it actually is.......unless I'm cycling and it feels about 20c hotter

 

[Sea of vapours]

You've missed off the next line of data, that being humidity. It's pretty humid and that's why it feels hotter. The same applies for cold: minus 30C in Siberia, for example, tends to feel a lot nicer than minus 10C in Yorkshire (from experience!).

 

[Fab Foodie]

You've missed off the next line of data, that being humidity. It's pretty humid and that's why it feels hotter. The same applies for cold: minus 30C in Siberia, for example, tends to feel a lot nicer than minus 10C in Yorkshire (from experience!).

Absolutely....
it's all to do with surface hear transfer.
As with wind chill, changes in Relative Humidity at both high and low temperatures have an impact on how we perceive heat.

 

[fossyant]

Sounds bliss. Glad I'm only on 11 days in Costa Del Sol as I melted a few days ago at 32c with no wind. Back home on Thursday. 20c yes please

 

[ColinJ]

I lopped off that bit but I did look at it and thought that the humidity was not especially high (in the 70%s). Here is the full version ...

 

[ColinJ]

Actually, I don't know what number is 'high' for humidity. I have seen it in the 90s and conditions feel horrid then!

 

[Sea of vapours]

Mid 70%s and above always feels a bit sticky to me. Certainly 90%s is very unpleasant so somewhere in that range is starting to become unpleasant.

 

[ColinJ]

Well, I'll go out and put it to the test now!

It's depressingly gloomy for July but probably very good for cycling.

 

[Fab Foodie]

As with many things in life there are always more complexities to something than it seems. Relative Humidity is one of those things as it's a ratio that is determined by how much moisture there is in the air at a given temperature over the Maximum amount of moisture that the air can hold at that temperature.
Also our bodies do not respond to the interaction of Temperature and Humidity in a linear fashion either!

 

[Blue]

When moving around outdoors one is often in direct sunlight. Aren't forecast temps "in the shade"?

 

[ColinJ]

I'm back from my ride and was thinking about all of this and noting how warm/cool/hot I felt at different times.

The temperature in my house in the shade was about 19 degrees and that was what it felt like. It didn't feel particularly humid indoors, but I wasn't doing very much so I wasn't generating lots of surplus body heat which needed to be sweated away..

When I headed out on my bike, I still felt comfortable for about 4 or 5 km of gentle riding, but then I turned onto a stonking climb which has significant stretches of 15-20% (Pudsey Rd/Shore Rd from Cornholme). I got very warm, very quickly. I was moving slowly and there wasn't much wind, and the humidity seemed to be stopping the sweat evaporating so it was dripping off me instead. Those who paid attention during their school science classes might remember the Latent Heat of Evaporation? Simply - the heat taken to turn a liquid to a gas at the same temperature. If the sweat is dripping rather than evaporating, it isn't doing much to cool you down, hence muggy days feeling warmer.

Once I had climbed onto the high roads and then begun a long rapid descent, I was effectively creating my own cooling wind. So effective was it that I needed to zip up my jersey and gilet to avoid feeling chilled.

So, yeah - humidity - that's the explanation!

 

[classic33]

When moving around outdoors one is often in direct sunlight. Aren't forecast temps "in the shade"?

Shade & still air temperatures. Which is why they say during the colder months that it will feel colder.

 

[Pat "5mph"]

Maybe I'm talking rubbish, but to me 20 Celsius here in Scotland feel much hotter than 20 Celsius when I was living in Italy.
I think it has something to do with the angle of the rays of the sun at different latitudes.
Or maybe it's because I'm just not used to good weather anymore!

 

[ColinJ]

Maybe I'm talking rubbish, but to me 20 Celsius here in Scotland feel much hotter than 20 Celsius when I was living in Italy.
I think it has something to do with the angle of the rays of the sun at different latitudes.
Or maybe it's because I'm just not used to good weather anymore!

I imagine that Scottish humidity is generally a lot higher than Italian humidity!

I am not a fan of high temperatures but I found 25-30 C not too bad in southern Spain, after a few days to get used to it. I'm sure that the humidity was low there. (It certainly didn't rain very often.)