# Heat Index and Riding



## gigem88 (May 10, 2011)

Thanks for the info.


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## pintophile (May 18, 2011)

If I'm going to ride in midday, I only walk. That never seems to do any sort of damage-she's still eager and bright-eyed afterwards, and the only places she sweats are under the tack areas.

I do all my trotting and cantering work at sunset, though.


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## Zimpatico (Nov 5, 2010)

Heat index of 120 seems a little high before being cautious, doesn't it? It's reported to be a heat index of 105 - 107 today in eastern PA. Althought, it might be a different calculation than what's stated above. The temp is reaching 100 degrees and the humidity is 42%, so that would be a heat index of 142 according to the calculation above. I just checked the heat advisory warnings from the national weather service, and they are reporting heat index as 105 - 110.

Just be aware that your news reports may refer to the heat index as different calculations...


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## wetrain17 (May 25, 2011)

kitten_Val said:


> Summer riding reminder
> 
> _The Heat Index is the sum of the temperature plus the humidity._
> *For example:*if the temperature is 80 degrees Fahrenheit and the humidity is 20%, then the Heat Index is 100 (80+20=100). If the Heat Index is less than 120, it is ok to ride. Start watching it as it rises above 120, at 150 your horse's cooling system won't work effectively. If it is greater than 180, your horse will be unable to thermo-regulate.​


​ The formula for figuring out the heat index is actually very complicated. You do not just add the temp and the humidity. I copied and pasted the formula for figuring out the head index. as you can see it is far easier to go to weather.com where the have it already set up. All you have to do is enter the temp and humidity and then hit "calculate".








where







= heat index (in degrees Fahrenheit)







= ambient dry-bulb temperature (in degrees Fahrenheit)







= relative humidity (in percent)


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## sarahver (Apr 9, 2010)

Thanks KV! I was just thinking about this today!



wetrain17 said:


> [/INDENT][/INDENT]
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OK, but looking at that formula, KV's estimation (key word being estimation) really shouldn't be that far off given that c1-c8 are constants and the equation itself appears to be logarithmic? As is (roughly) the mathematical relationship that KV describes?

Just a thought :wink:


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## Jake and Dai (Aug 15, 2008)

May I just say I now have a headache that has nothing to do with the actual heat index and everything to do with reading that formula? HAHAHAHAHA


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## pintophile (May 18, 2011)

sarahver said:


> Thanks KV! I was just thinking about this today!
> 
> 
> 
> ...


:shock:

...uh...


What? :lol:


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## sarahver (Apr 9, 2010)

pintophile said:


> :shock:
> 
> ...uh...
> 
> ...


Heh. Nerd status of Sarah: CONFIRMED.

Basically I think that KV's estimation holds reasonably true to the model :wink:


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## RATHER BE RIDING (Dec 7, 2010)

That is good to know. It is hard to ride them when they are sweating standing still, but I have a couple that really need to get back in shape and I was just wondering at what point I should not ride. Thanks!


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## wetrain17 (May 25, 2011)

the example of add the 80 and 20 is not far off. Take my area today. The temp is 98 and the humidity is 50. if you add them it equals 148; however plug it into a formula and you get 112 and that is a big difference.


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## mbender (Jul 22, 2009)

E=MC2. I just know when its hot and I'm drenched doing absolutely nothing outside and so is my horse, there's probably a concern for not riding much.
_Posted via Mobile Device_


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## serafina (May 5, 2011)

I think there's a big problem with this approach - not just because the term "heat index" is getting misused - but because it's using the air temp and the relative humidity. The relative humidity is a joint function of the air temp and the *dewpoint*. The dewpoint is going to tell us how comfortable we'll (and presumably, the horse) at any given temp.

Here's an illustration of the problem:
Tomorrow morning, wunderground forecasts a dewpoint of 74 at 9am, 72 at 11am, and 65 at 2pm. All of these numbers are pretty high, and mean that it is going to be pretty nasty and sticky here tomorrow, just like today. Ugh.

At those same times, the air temps are forecast to be 79, 88, and 95.
Relative humidities are forecast to be 82%, 57%, and 37%. This has to do with the difference between the air temp and the dewpoint - so 37% relative humidity at 95 is going to feel SUPER gross, and the only reason I'd go to a barn under those conditions is to check the water, maybe hose off the horses, make sure everyone is still alive. 

Yet - here's the kicker - even though tomorrow's sauna-like nastiness is going to be increasing markedly through the day, thanks to high dewpoints and rising temps, the numbers you'd get from the vet's calculations are going to be *sinking*, implying that it will be getting *easier* for the horse to work as the day goes along, not *harder,* which I promise it will be. 

According to the vet's reference ranges, working the horse at 9am when it is not 80 degrees outside yet will put more of a strain on him that it will at 2pm when it's starting to push 100 degrees and is VERY humid. In fact, holding the dewpoint constant (it's not, but it's pretty close since we are not lucky enough to have that cool front in our forecast tomorrow) - holding the dewpoint constant, according to this vet's recommendation, *the hotter it is, the safer it is to work the horse.*

That's not right.

PS, Here is a great site with a chart of dewpoints that lets you know how comfortable you are likely to be at a given dewpoint.


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## kitten_Val (Apr 25, 2007)

pintophile said:


> I do all my trotting and cantering work at sunset, though.


I can't even do that. It's SO bad here this week that sunset is not much better. I ride 30 mins very early in morning (like 7:30 - 8 am). Then I barely can drag my own feet... :-(


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## kitten_Val (Apr 25, 2007)

Jake and Dai said:


> May I just say I now have a headache that has nothing to do with the actual heat index and everything to do with reading that formula? HAHAHAHAHA


LOL! Yes, I'm sure temp + humidity as an index is not 100% correct. But I think it's given more as an estimation rather than something to rely on completely. :wink: 

I did go to LV couple year back. Could move around all day in 100F (I did ATV, walked around the city, etc. etc.). Because there was no humidity. We have 100F now here in MD. It's HORRIBLE. 

So basically if it's hot for me to the point I feel like I gonna fall - I don't ride. If it's so bad on me, I can only imagine how bad it'll be on my horse (with all my pounds on back).


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## mbender (Jul 22, 2009)

^^^ agreed 100%
_Posted via Mobile Device_


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