How Hot is Too Hot?

Mother Nature is not yet done roasting us with the summer sun. We’ve had a good week or two of cool weather but now Philly is roasting hot. Factoring in humidity, it feels a little over 100 Degrees Fahrenheit outside. Put another way, if we cracked an egg on the hood of lead salesman Scott’s Jeep, it’d probably turn to dust in about a minute. The US National Weather Service has issued heat advisories and warnings to stay inside. Where do we put that boundary, between mere comfort and necessity to live?


Beyond Uncomfortable

When we start to see these excessive temperatures proper cooling becomes not a matter of comfort, but of health, life, and death. When the Heat Index breaks past 100 degrees, we start to have issues cooling ourselves. The core of your body wants to be at about 98 degrees. If the air outside of you is above 98 degrees, it can be physically impossible to remain cool.

In these situations, any movement or activity outside can make you hotter. The hotter you are, the more you sweat. The more you sweat, the more dehydrated you are. At the same time, excessive humidity will make sweating less and less effective at cooling your body. At some point, it just becomes impossible to remain healthy. You’ll either become too dehydrated or start to suffer heat-stroke and exhaustion from your body becoming too hot.

These situations are more common on Earth than we’d like. Places like Phoenix, Arizona will see multiple days above 110 degrees in any given year. There are places where living a healthy life may be near impossible without some form or air conditioning or cooling.


Getting a Temperature

In order for us to have these concerns, we first need to understand the real temperature. To do this, we need a Heat Index. The air temperature might be 90 degrees, but with enough humidity, that 90 degrees can be made to feel closer to 100 or 110 degrees. That is a problem. Although the air is relatively cool, our body’s cooling system is unable to perform well in high humidity. The air might be 90 degrees, but because we are incapable of sweating out the heat, our bodies will be far, far hotter.

Helpfully, the National Weather Service has a chart published on their site that shows the perceived temperature in various conditions:

Heat Index Chart

Mother nature can turn a relatively cool 88 degree day into a near life threatening 121 degrees. When we determine what warnings to issue, charts like this are the first thing we turn to.


Getting a Warning

These excessive heat warnings are done on a regional basis, county by county. It is possible to drive a few miles and experience significantly cooler temperatures or lower humidity. Warnings are given on as local a basis as possible.

This also means heat warnings take the local climate into account. In PA, anything over 100 degrees will trigger a warning or watch from the National Weather Service. In the south however, a place like Texas, 100 degrees is a fact of life. People in the area are already aware of that hazard, they’re likely even a little acclimated and tolerant of it from constant exposure. Such heat advisories might not be issued til’ the temperatures break 105 or 110 degrees in those areas.


What Does This All Mean?

This all adds up to a couple conclusions for you:

  1. If you live somewhere where it gets hot, buy AC.
  2. If you get any kind of heat warning or advisory, don’t be active, stay cool
  3. Excessive heat can be a life and death situation

These are conclusions you probably already knew, but now you, like us, know some of the science and set up behind the extreme heat around you. It’s all local warnings, they factor in what your environment is like, and AC is a good thing.


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