Heat Index
How Hot Is It In Phoenix?
When considering the temperature, it is also important to keep the Heat Index in mind.
What is the Heat Index?The Heat Index is the temperature the body feels when humidity is taken into account.
Phoenix: Is It Really a Dry Heat?
You've certainly heard the phrase, "It's a Dry Heat." Some people
think that this is the Phoenix city motto! You can even find it on tee shirts.
The truth is that because our humidity levels are lower than in some other parts
of the country, 100° may not feel as terrible as in some parts of the
country that have higher levels of humidity.
Why Does it Feel Hotter When it Is More Humid?
When the humidity is high, we don't sweat as much, and so our body loses some of
the cooling effect that sweating provides.
Is a High Heat Index Dangerous?
People can be affected by heat even when the temperatures aren't that high, but
certainly when the Heat Index gets into the blue zone in the chart below, people
are at higher risk of heat exhaustion and
heat stroke.
| Temperature vs. Relative Humidity: Heat Index | ||||||
| °F | 90% | 80% | 70% | 60% | 50% | 40% |
| 80 | 85 | 84 | 82 | 81 | 80 | 79 |
| 85 | 101 | 96 | 92 | 90 | 86 | 84 |
| 90 | 121 | 113 | 105 | 99 | 94 | 90 |
| 95 | 133 | 122 | 113 | 105 | 98 | |
| 100 | 142 | 129 | 118 | 109 | ||
| 105 | 148 | 133 | 121 | |||
| 110 | 135 | |||||
How High Does the Humidity Get in the Summer in
Phoenix?
When it is 100° or higher, the highest humidity level for the past hundred
years was 45%. Usually, it's significantly lower than that.
Is Humidity Rising in Phoenix?
Many people think that because the population is increasing so rapidly, and
there are more lawns and more pools, that humidity levels are also rising.
Studies have shown that actually the opposite is true. More pavement and related
urbanization have meant that in recent years humidity levels
have actually decreased.
So 110°
Doesn't Feel So Bad, Right?
I saw this comment in a blog on the Internet, and I thought it answered this
question admirably:
The phrase "yeah, but it's a dry heat" is most often muttered by people who have never actually spent a summer at 115 +. Eggs frying on the sidewalk is only a myth because chickens are too smart to be outside during the summer in Arizona. "Yeah, but it's a dry heat." So is the surface of the sun, but I aint about to move there either. (Jim)
Seriously, though, there are few days that reach 115° but it does happen. Here's is some triple digit trivia for you to enjoy! Also, you might want to know--can you really fry an egg on the sidewalk on those hot Phoenix days?
Heat Index Chart provided courtesy of the National Weather Service.
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