Is It Too Hot To Play Outside?

[Guest greytexplorer]

A friend of mine (horse and grey savvy) offered the following information to me about knowing when it's ok/not ok to be out and about in this miserable heat. (We are at day 9 of 100+ temps, and expected to go 12 days before any break in the heat)

Because I had gotten heatsick over the weekend, she suggested I follow it too!

I equate the word "ride" to "play outside". Hope you find this useful. I did!

 

 

Here's a rule of thumb for Sighthounds taken from the "Horseback riding rule of thumb".

The same can be said about how Sighthounds cool themselves and how long they should be outside playing or being taken to parks.

 

Add air temperature and relative humidity and subtract wind speed.

If your total adds up to 180 or above don't ride, if it is 130-170 use

caution, 130 or below ride!

 

Determine: Temperature (F) + relative humidity (%) – wind speed

For example:

Temperature (F) 79

Relative Humidity (%) 58

Wind Speed 4.6 (MPH)

Answer = 132.4

 

Less than 130: All go—horses can function to cool themselves assuming

adequate hydration.

130 – 170: Caution—a horse's cooling mechanisms can only partially

function as intended. Some cooling management procedures will need to

be performed.

180 or above: Stop—a horse's cooling systems cannot and will not

function adequately. All cooling procedures will need to be utilized

to keep the horse out of serious trouble.

 

Why is it an issue for the horse when heat and humidity combine to

equal 180+? What doesn't work and why? What are some of the

physiological ramifications? What are some of the symptoms?

Heat is produced by muscles in the metabolic conversion of chemical

energy to the mechanical energy required for muscle contraction and

limb movement. Seventy-five to eighty percent of the chemical energy

is converted to heat, which moves from the contracting skeletal

muscles to the surrounding tissues by the flow of lymph and blood.

Assuming a comparable rate of exercise intensity, the rate of

cooling, or heat loss is affected by air temperature, wind velocity

and humidity. (Werner, 1993). Heat can also be lost in a fourth way,

conduction, which is a direct transfer of heat from the skin or feet

to surfaces in direct contact (such as an ice bag on the skin).

 

So, thinking about the chart and the equation:

Temperature (F) + relative humidity (%) – wind speed (MPH), we see

how the ability of the horse to cool itself in these four different

ways will be affected:

 

• In cool temps with low humidity, heat loss through convection and

conduction can be as much as 50%. Heat can also be lost through

radiation, with as much as 60% of a body's heat lost in this way when

air temperatures are cool. The numbers in our equation would add up

to much less than 180, and the horse would have no difficulty cooling

itself.

• As temperatures rise, the thermal gradient for heat dissipation is

reduced, resulting is less convective, conductive and radiative heat

loss and more evaporative cooling. The evaporation of water from the

skin surface is the most important means of heat dissipation in high-

heat/low-humidity conditions. So, when we get a high temperature

reading with low humidity, a horse may still not have difficulty

cooling, but if temperatures are extremely high with no wind, we

might get a result above 140, which would means our horse needs our

help cooling off.

• With high humidity, sweat cannot evaporate as easily and so the

ability of the horse to cool itself in this important way is reduced.

When high humidity is combined with high temperatures, (which we just

saw reduce the effectiveness of radiant, conductive and convective

cooling), the horse has now lost all four means to cool itself and is

in a dangerous situation, subject to a greater rate of heat

accumulation within his body.

[ZoomDoggy]

Or one could use my simpler equation: If it feels yucky, we don't go out.

[Guest greytexplorer]

Or one could use my simpler equation: If it feels yucky, we don't go out.

 

so zoomdoggy, how yucky could it possibly be in MN?

[Jiffer]

That's pretty neat. I just did our day today and the number is 121.57.

[Guest rsqdogsmom]

My feeling, if I have to ASK the answer is "YOU BET!"

[ZoomDoggy]

Or one could use my simpler equation: If it feels yucky, we don't go out.

 

so zoomdoggy, how yucky could it possibly be in MN?

 

Ha, you laugh, but my blood has become thick up here. When it's in the high 90's with a dewpoint of 70+, We're wilting.

 

But then I'm just as intolerant of our extreme cold too. Why oh why can't autumn last longer??

[MarcR]

If I open the door, and start looking for the spa attendant with the towels, it's too hot

[LBass]

That is interesting. I tried out the formula on our weather today: 102 + 25 - 5 = 122 (102 degrees with 25% humidity and 5 MPH wind).

Based on that, we should be good to play actively with no worries, but it is 102 degrees outside and I just can't believe that Piper would be safe playing actively outside in that heat (and I know that if he wants to, he'll do it all by himself, 'cause I'm staying in the A/C!).

[Chicocat]

I have an easier formula. If it's close to 90 or more, they don't need to be out there. Most of the time they agree.

[Guest TBSFlame]

90 and above is my rule. It is 10 here today. Too hot for me outside and the hounds agree.

[Guest SusanP]

Our current temp is 74, humidity 88, wind 7 = 155. But it honestly doesn't seem so bad out there, especially after all the heat and humidity we just had until yesterday!

 

My fallback formula is: If the dogs are barely moving, I don't walk them very far. If they want to come in from the yard, I let them in!

Edited August 16, 2007 by SusanP

[turbotaina]

I don't think that I'd use the same formula for greyhounds as for horses. Remember, horses sweat, dogs have to pant so it's not as efficient.

 

 

[greyhounds1234]

That is interesting. I tried out the formula on our weather today: 102 + 25 - 5 = 122 (102 degrees with 25% humidity and 5 MPH wind).

Based on that, we should be good to play actively with no worries, but it is 102 degrees outside and I just can't believe that Piper would be safe playing actively outside in that heat (and I know that if he wants to, he'll do it all by himself, 'cause I'm staying in the A/C!).

 

Similar problem here...99 degrees, 23% humidity, 10 mph windspeed =no way my dogs would want to be outside for more than just a quick potty break.

 

Patti