Heat and humidity can create life threatening conditions during the Summer. Read more about it below.
Experimental NWS HeatRisk
In the picture: The National Weather Service experimental HeatRisk tool combines weather, climate, and Centers for Disease Control and Prevention (CDC) data to identify potentially dangerous heat.
The National Weather Service HeatRisk tool is an experimental color-numeric-based index that expresses a likelihood of heat-related impacts to occur over a 24-hour period. HeatRisk takes into consideration: (1) how unusual the heat is for the time of the year, (2) the duration of the heat including both daytime and nighttime temperatures, and (3) if those temperatures pose an elevated risk of heat-related impacts based on data from the Centers for Disease Control and Prevention (CDC).
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").
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.
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.
In the pictures: Examples of wet bulb globe temperature (WBGT) charts used by the Arkansas Activities Association and the military to schedule rest and/or hydration as readings climb into the 80s to over 90 degrees.
In the picture: The Wet Bulb Globe Temperature (WBGT) was in the upper 80s to around 90 degrees at a junior high school football field on the west side of Jacksonville (Pulaski County) between 500 pm and 600 pm CDT on 08/09/2020. The air temperature was in the mid 90s, with a relative humidity at 50 percent (dewpoint temperature 74 degrees/wet bulb temperature 81 degrees), a south wind close to 8 mph, and a globe temperature around 115 degrees. Given the conditions, it was a very uncomfortable afternoon to be outdoors.
A key difference between HX and WBGT is the timing of potentially life threatening conditions. While such conditions will usually not materialize until the afternoon with HX (as temperatures climb above 90 degrees), critical WBGT numbers may be realized in the morning (temperatures in the 80s).
That is because the wet bulb temperature (Tw) is a heavily weighted component in the WBGT calculation, and is an indication of how much humidity is present. A high Tw means there is a lot of humidity (and a very uncomfortable situation), and it does not have be hot to make this happen.
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.
Hot Cars
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.
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.
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.
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.
To help you protect yourself, check out the UV (i.e. ultraviolet) Index links below.
Follow us on Twitter
Follow us on Facebook
Follow us on YouTube
LZK RSS Feed