National Weather Service United States Department of Commerce
Heat Wave
Hot Weather
Heat and humidity can create life threatening conditions during the Summer. Read more about it below.
 
The Heat and Your Body
 

When the summer months arrive in Arkansas, the heat can become unbearable at times. Factoring in high humidity, it feels warmer than it actually is. More specifically, the body is not able to cool as effectively through sweating.

On a dry day, sweat evaporates into the air, which creates cooling. Adding moisture to the atmosphere cuts down on evaporation. Over time, the body temperature rises and shuts down.

Heat is the number one weather related killer across the country (more than hurricanes, floods, lightning and tornadoes).

The "heat index" considers the effects of heat and humidity. When these variables combine to make it feel like 105 degrees or greater, it is considered dangerous.

 
HEAT INDEX °F
  RELATIVE HUMIDITY (%)
TEMP (°F) 40 45 50 55 60 65 70 75 80 85 90 95 100
110 136                        
108 130 137                      
106 124 130 137                    
104 119 124 131 137                  
102 114 119 124 130 137                
100 109 114 118 124 129 136              
98 105 109 113 117 123 128 134            
96 101 104 108 112 116 121 126 132          
94 97 100 103 106 110 114 119 124 129 135      
92 94 96 99 101 105 108 112 116 121 126 131    
90 91 93 95 97 100 103 106 109 113 117 122 127 132
88 88 89 91 93 95 98 100 103 106 110 113 117 121
86 85 87 88 89 91 93 95 97 100 102 105 108 112
84 83 84 85 86 88 89 90 92 94 96 98 100 103
82 81 82 83 84 84 85 86 88 89 90 91 93 95
80 80 80 81 81 82 82 83 84 84 85 86 86 87
A Heat Index Chart is shown above. For an image, click here.
 

For example, using the chart above, a temperature of 96 degrees with a relative humidity of 50% net a heat index of 108 degrees. Other than the chart, try using our meteorological calculator by clicking here.

When heat index values meet or exceed 105 degrees over a fairly large area (and/or temperatures are 103 degrees or greater), the National Weather Service will usually issue a Heat Advisory.

When heat index values reach 110 degrees over a fairly large area (and/or temperatures are 105 degrees or greater), an Excessive Heat Warning may be posted.

 
Current Heat Index (HX) Values Across Arkansas
 
Hourly Weather Roundup ( )
Location Temperature Relative Humidity Heat Index
Fayetteville
N/A
N/A
HX N/A
Harrison
N/A
N/A
HX N/A
Mountain Home
N/A
N/A
HX N/A
Jonesboro
N/A
N/A
HX N/A
Fort Smith
N/A
N/A
HX N/A
Russellville
N/A
N/A
HX N/A
Mount Ida
N/A
N/A
HX N/A
Hot Springs
N/A
N/A
HX N/A
Little Rock
N/A
N/A
HX N/A
West Memphis
N/A
N/A
HX N/A
Texarkana
N/A
N/A
HX N/A
El Dorado
N/A
N/A
HX N/A
Pine Bluff
N/A
N/A
HX N/A
Monticello
N/A
N/A
HX N/A
Note: In the HEAT INDEX column, HX is "heat index" (if shown). For HX to be displayed, TEMPERATURE and RELATIVE HUMIDITY must be available (not "N/A" or "MISG").
Below Criteria: 
 y 
Near Heat Advisory Criteria: 
 o 
Heat Advisory Criteria: 
 r 
Excessive Heat Warning Criteria: 
 p 
 
 
Comparing WBGT and Heat Index
Variable WBGT Heat Index
Measured in the sun x
Measured in the shade x
Uses Temperature
Uses Relative Humidity
Uses Wind x
Uses Cloud Cover x
Uses Sun Angle x

Other than the heat index (HX), the wet bulb globe temperature (WBGT) is being used more and more by athletic programs as a safety measure to prevent heat related illnesses. The WBGT was invented in the 1950s due to a number of heat casualties occurring in the United States armed services (especially during military training). After implementing WBGT, there was a drastic reduction in heat illnesses/deaths.

Just like the HX, WBGT is derived from ambient temperature and relative humidity. However, the effects of wind and solar radiation are also considered when calculating WBGT. Maximum WBGT values are achieved in full sun and with little wind. To measure WBGT accurately, a heat stress tracker (that monitors WBGT) is recommended.

 

Links of Interest
More About WBGT and How It Is Monitored (courtesy of the Korey Stringer Institute at the University of Connecticut)
WBGT: The Wet Bulb is the Key

 

In the video: This is a guide to wet bulb globe temperature (WBGT), and developing a plan to exercise diligently in the heat. The video is courtesy of the Korey Stringer Institute at the University of Connecticut.
 

Since HX and WBGT are determined differently, their values and what they mean are not the same. HX becomes dangerous at 105 degrees or more, with WBGT just as unsafe in the upper 80s to around 90 degrees. In addition, charts are being developed for values of WBGT that take into account activity stress levels (such as light, moderate, or hard work), and the amount of rest and fluid to consume when participating in these activities.

 

An example of a wet bulb globe temperature (WBGT) chart used by the military to schedule rest and hydration as readings climb into the 80s to over 90 degrees.
In the picture: An example of a wet bulb globe temperature (WBGT) chart used by the military to schedule rest and hydration as readings climb into the 80s to over 90 degrees.

 

Hourly Weather Roundup ( )
Location Estimated WBGT Heat Index
Fayetteville
WBGT N/A
HX N/A
Harrison
WBGT N/A
HX N/A
Mountain Home
WBGT N/A
HX N/A
Jonesboro
WBGT N/A
HX N/A
Fort Smith
WBGT N/A
HX N/A
Russellville
WBGT N/A
HX N/A
Mount Ida
WBGT N/A
HX N/A
Hot Springs
WBGT N/A
HX N/A
Little Rock
WBGT N/A
HX N/A
West Memphis
WBGT N/A
HX N/A
Texarkana
WBGT N/A
HX N/A
El Dorado
WBGT N/A
HX N/A
Pine Bluff
WBGT N/A
HX N/A
Monticello
WBGT N/A
HX N/A
Note: In the HEAT INDEX and Estimated WBGT columns, HX is "heat index" and WBGT is "wet bulb globe temperature" (if shown). For values of HX and Estimated WBGT, TEMPERATURE and RELATIVE HUMIDITY must be available or "N/A" will be displayed. WIND and SKY CONDITIONS are also factored into WBGT, with (w) or (s) shown if either are missing. If both are missing, (w,s) will follow WBGT, and it is assumed there is full sun with nearly calm conditions. For the most accurate readings of WBGT, a heat stress tracker (that monitors WBGT) is recommended. Such a tracker was not used in the estimates above.
 
*** WBGT forecasts below are experimental and may not always be available. ***
Day 1 WBGT Forecast (700 am to 100 pm)
In the picture:  Click to enlarge.
Day 1 WBGT Forecast (100 pm to 700 pm)
In the picture:  Click to enlarge.
 
Day 2 WBGT Forecast (700 am to 100 pm)
In the picture:  Click to enlarge.
Day 2 WBGT Forecast (100 pm to 700 pm)
In the picture:  Click to enlarge.
 
Day 3 WBGT Forecast (700 am to 100 pm)
In the picture:  Click to enlarge.
Day 3 WBGT Forecast (100 pm to 700 pm)
In the picture:  Click to enlarge.
 
Hot Cars
 
To prevent heat deaths, remember to look before you lock.
In the picture: To prevent heat deaths, remember to look before you lock.
 

While summer heat is stifling enough just standing in the sun, it is even worse in a parked car. Your vehicle acts very much like a greenhouse. Energy from the sun goes through the windows and quickly heats the dashboard and seats, which in turn warm the surrounding air. Temperatures in the car can rise as much as 30 to 35 degrees in a half hour.

Small children can easily suffer from heatstroke when faced with these conditions. Their body temperatures warm three to five times as fast as an adult. Pets are also in big trouble considering many have a thick coat of fur.

Staying Cool
 
Drink plenty of fluids. If you are outside in the heat for any length of time, use some common sense and stay cool.  Why?  Heat can be deadly.  To avoid being a victim...drink plenty of non-alcoholic fluids.
 
Go to an air conditioned area periodically to help keep your body temperature down. Go to an air conditioned area.
 
If you have to be outdoors, wear light colored loose-fitting clothing and don't exert yourself too much. Remember to check on the elderly to make sure they are in a cool environment. Every year, someone succumbs to the heat. Don't let that someone be you.
 
Don't forget your pets!
Finally, don't forget about your pets! If you leave them outdoors, provide plenty of cool water and make sure there is a shady spot available.
 
Other Items
 
Other than the heat, there is one more item you might consider as you head outdoors. Too much exposure to the sun's ultraviolet rays could damage your skin.
 
Check the U.V. Index To help you protect yourself, check out the UV (i.e. ultraviolet) Index links below.
 
For more information about heat and heat safety from the National Weather Service, click here. Heat Wave Logo