Lake Charles, LA

Weather Forecast Office

Wet Bulb Globe Temperature Forecasts

EXCESSIVE HEAT: Wet Bulb Globe Temperature & Heat Index

The Wet Bulb Globe Temperature (WBGT) is an indicator of heat-related stress on the human body at work (or play) in direct sunlight. It takes into account multiple atmospheric variables, including temperature, humidity, wind speed, sun angle, and cloud cover.

The Heat Index is more commonly known and is used as an indicator of extreme heat and potential health-related impacts, but only takes into account temperature (measured in the shade) and relative humidity.

What value should you use? For day-to-day activities, the heat index will serve you well. If you work outside or are planning any sort of vigorous outdoor activity in the full sun, it is better to use the WBGT.

Additional heat resources (courtesy of NWS Springfield, MO) include the NWS Heat Tools two-pager and the NWS WBGT one-pager.

Wet Bulb Globe Temperatures by Parish or County
Select Parish/County: For more information on parish/county splits, click here.

Wet Bulb Globe Temperature & Heat Index

Lat=30.52 Lon=-93.05
Click on map to change

© OpenStreetMap contributors.

Initial values are estimates for the selected location. Adjust sliders as needed
Month:	3
Day:	24
Latitude:	30.5211
Fcst Max Temp(F):	80
DewPoint(F):	70
RH(%):	72
Wind Speed(mph):	10
Cloud Cover(%):	25

Heat Index (F):	88
WBGT (F):	88

Map, calculator courtesy National Weather Service - Tulsa

MAPS

Need HOURLY forecast maps for WBGT, Heat Index and other weather elements? Check this out.

Wet Bulb Globe Temps

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7 pm

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Thursday

Heat Index

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Wet Bulb Globe Temperature vs Heat Index

While the WBGT and Heat Index both attempt to describe how "hot" it is and the potential for heat-related stresses, they go about it in different ways.

Heat Index is more commonly used and understood by the general public - the higher the values, the hotter it's going to feel and the higher the threat for heat-related illnesses. It's calculated from the temperature and relative humidity. What's not commonly known is that Heat Index assumes you are in the shade.

WBGT also uses the temperature and humidity in its calculation, but temperatures are measured in direct sunshine. It also factors in wind speed, sun angle, and cloud cover.

Bottom-line upfront >>>> what value should you use? For day-to-day activities, heat index will serve you well. If you work outside or plan on any sort of vigorous outdoor activity in the full sun, use the WBGT.

Comparing WBGT and Heat Index

	WBGT	Heat Index
Measured in the sun
Measured in the shade
Uses Temperature
Uses RH
Uses Wind
Uses Cloud Cover
Uses Sun Angle

Examples

Temp F	Dew Point F	RH %	Sky %	Wind mph	Heat Index F	WBGT F
90	65	42	05	03	92	89
90	65	42	05	13	92	83
90	65	42	65	13	92	81
90	70	52	10	06	96	88
90	70	52	60	06	96	86
90	70	52	60	13	96	85
100	70	39	10	13	108	90
100	70	39	10	5	108	94
100	70	39	65	05	108	91

WBGT		Heat Index
Origins: The WBGT date back to the 1950s - specifically the United States Marine Corp Recruit Depot on Parris Island, SC. There, recruits were required to perform high intensity exercise in a high humidity, high temperature environment. Many solders succumbed to heat related illness. In response, a joint effort between the Department of the Navy and Army doctors studied the effects of heat on exercise performance. The result was the WBGT. WGBT uses several atmospheric variables for its calculations: temperature, humidity, wind speed, sun angle, and cloud cover. Temperatures are measured in the sunlight. The military uses the WBGT to gauge the potential for heat related stresses to this day. OSHA and many nations also use the WBGT as a guide to managing workload in direct sunlight, as do athletic departments (college and high school) and events. If you work or exercise in direct sunlight, this is a good element to monitor.		Origins: The Heat Index is based on work carried out by Robert G. Steadman in 1979 ("An Assessment of Sultriness, Parts I and II") where he discussed factors that would impact how hot a person would feel under certain conditions. The National Weather Service developed a "simplified" formula from this work using air temperature and relative humidity as the two inputs. This formula became the "heat index". It is important to note that the heat index is calculated for shady areas. Direct sunlight can add as much as 15 degrees to the heat index.
Inputs: Temperature (in sun) Relative Humidity Wind speed Cloud cover Sun angle		Inputs: Temperature (in shade) Relative Humidity
Equation: WBGT=0.7T_w+0.2T_g+0.1T_d T_w is the wet bulb temperature, which indicates humidity T_g is the globe temperature, which indicates radiant heat T_d is the ambient air (dry) temperature		Equation: Heat Index = -42.379 + 2.04901523T + 10.14333127R – 0.22475541TR – 6.83783(10^-3T²) – 5.481717(10^-2R²) + 1.22874(10^-3T²R) + 8.5282(10^-2TR²) – 1.99(10^-6T²R²) T = ambient dry temperature (in Fahrenheit) R = relative humidity (percentage) For more information on the heat index: Heat Index Heat Index Climatology

PREPARE - SAFETY - RESOURCES

Prepare

Before:

Reschedule or postpone outdoor plans during peak heating of the day (usually mid to late afternoon)
Check in with family members, friends. Make sure they have a way to keep cool and take necessary precautions from the heat. The elderly and children are especially susceptible to the heat.
Don't forget your pets! Make sure they have adequate shelter (preferably indoors, air conditioned) and ample water.

During:

Take frequent breaks in the shade or in an air conditioned location. Strenuous outdoor activities should be reduced (or eliminated), especially in direct sunlight where there is little ventilation.
Drink plenty of water or other non-alcohol fluids. Stay hydrated by drinking plenty of fluids even if you do not feel thirsty. Avoid drinks with caffeine or alcohol.
Continue to check on family, friends and your pets.
Don’t get too much sun. Sunburn makes the job of heat dissipation that much more difficult

Resources

General WBGT Information (Wiki page)
American College of Sports Medicine (ACSM), [position stand]
Korey Stringer Institute
University of Georgia Research [AMS conference presentation]
WBGT Research (courtesy of NWS Tulsa)
OSHA Heat Hazard Assessment and WBGT
Department of the Army: Heat Illness & WBGT, Guidelines, Prevention

WBGT Guidelines - Charts

While there is not set criterion for WBGT temperatures and related risks/impacts, the American College of Sports Medicine (ACSM) has developed a set of values that have been accepted as a standard to follow. Their original guidelines were developed for running events, but have since been expanded to include intermittent (non-continuous) activities [Medicine & Science in Sports & Exercise: March 2007 - Volume 39 - Issue 3 - p 556-572] . The guidelines are not based on location.

Using ACSM as a starting point, further research by the University of Georgia (UGA) factored in climatology and regional differences in an effort to incorporate acclimatization* into the guidelines. The Korey Stringer Institute and USA Soccer used the regional categories developed by UGA to provide another set of recommend actions.

The military and OSHA also have devised recommendations, as do many university and high school athletic departments.

Below you will find several of these guidelines/recommendations.

It should be noted that while WBGT will provide solid guidelines, other factors such as an individual’s physical fitness, acclimatization, medical condition, and age also have an impact.

* Acclimatization: the body's natural adaptation to heat/cold. The process usually takes 10 to 14 days.

NOT based on location - American College of Sports Medicine

Continuous Activities		Intermittent Activities
Activities with little if any break, such as cross country running, 5K runs, and marathons.		Activities that generally have breaks between bursts of high intensity movements/actions, such as football, soccer, lacrosse, etc.

Guidelines from the American College of Sports Medicine - not based on location		Guidelines from the American College of Sports Medicine - not based on location

Based On Location

The following recommendations use similar criteria as the ACSM, but modified for location and climatology. This adjustment factors in the acclimatization that occurs for those that consistently work and exercise in hot environments.

Regional Categories



Guidelines from USA Soccer and the Korey Stringer Institute (KSI)		Guidelines from the University of Georgia

Other Charts For Reference

wbgt recommendations
A composite of various guidelines and recommendations for those working or exercising in full sun

Work and Rest Water Consumption Table
U.S. Military Recommendations, also used by OSHA

Military Flag Stress Conditions

Heat Index Guidelines - Charts

How to read the chart: find the temperature on the left hand side, then move to the right until you find the column for the approximate relative humidity. That number will be the temperature that it will "feel" like. Example: A temperature of 95 and relative humidity of 50% will "feel" like 107 degrees.

	0%	5%	10%	15%	20%	25%	30%	35%	40%	45%	50%	55%	60%	65%	70%	75%	80%
115	103	107	111	115	120	127	135	143	151
110	99	102	105	108	112	117	123	130	137	143	151
105	95	97	100	102	105	109	113	118	123	129	135	142	149
100	91	93	95	97	99	101	104	107	110	115	120	126	132	136	144
95	87	88	90	91	93	94	96	98	101	104	107	110	114	119	124	130	136
90	83	84	85	86	87	88	90	91	93	95	96	98	100	102	106	109	113
85	78	79	80	81	82	83	84	85	86	87	88	89	90	91	93	95	97
80	73	74	75	76	77	77	78	79	79	80	81	81	82	83	85	86	86
75	69	69	70	71	72	72	73	73	74	74	75	75	76	76	77	77	78
70	64	64	65	65	66	66	67	67	68	68	69	69	70	70	70	70	71

IMPORTANT: Heat index values were devised for shady, light wind conditions. Exposure to full sunshine can increase values by up to 15 degrees! Also, strong winds, particularly with very hot, dry air, can be extremely hazardous.

Or, if you know the temperature and the dewpoint OR relative humidity, figure out the heat index using the calculators below.

HEAT INDEX using Temp and Dew Point

HEAT INDEX using Temp and RH

Dew Point vs. Humidity

The dew point is the temperature the air needs to be cooled to (at constant pressure) in order to achieve a relative humidity (RH) of 100%. At this point the air cannot hold anymore water in the gas form. If the air were to be cooled even more, water vapor would have to come out of the atmosphere in the liquid form, usually as fog or precipitation.

The higher the dew point rises, the greater the amount of moisture in the air. This directly effects how "comfortable" it will feel outside. Many times, relative humidity can be misleading. For example, a temperature of 30 and a dew point of 30 will give you a relative humidity of 100%, but a temperature of 80 and a dew point of 60 produces a relative humidity of 50%. It would feel much more "humid" on the 80 degree day with 50% relative humidity than on the 30 degree day with a 100% relative humidity. This is because of the higher dew point.

So if you want a real judge of just how "dry" or "humid" it will feel outside, look at the dew point instead of the RH. The higher the dew point, the muggier it will feel.

General comfort levels that can be expected during the summer months:

less than or equal to 55: dry and comfortable
between 55 and 65: becoming "sticky" with muggy evenings
greater than or equal to 65: lots of moisture in the air, becoming oppressive

Heat Index/Heat Disorders

Heat Index	Possible heat disorders for people in higher risk groups
80-90	Fatigue possible with prolonged exposure and/or physical activity.
90-105	Sunstroke, heat cramps and heat exhaustion possible with prolonged exposure and/or physical activity.
105-130	Sunstroke, heat cramps or heat exhaustion likely, and heat stroke possible with prolonged exposure and/or physical activity.
130 or higher	Heatstroke/sunstroke highly likely with continued exposure.

Heat Disorder	Symptoms	First Aid
Sunburn	Redness and pain. In severe cases swelling of skin, blisters, fever, and headaches.	Ointments for mild cases if blisters appear and do not break. If breaking occurs, apply dry sterile dressings. Serious, extensive cases should be seen by a physician.
Heat Cramps	Painful spasms usually in muscles of the legs and abdomen possible. Heavy sweating.	Firm pressure on the cramping muscles, or gentle massaging to relieve the spasm. Give sips of water. If nausea occurs, discontinue use.
Heat Exhaustion	Heavy sweating, weakness, skin cold, pale and clammy. Pulse thready. Normal temperature possible. Fainting and vomiting.	Get victim out of sun. Lay down and loosen clothing. Apply cool, wet cloths. Fan or move victim to air conditioned room. Sips of water. If nausea occurs, discontinue use. If vomiting continues, seek immediate medical attention.
Heat Stroke (sunstroke)	High body temperature (106 F or higher). Hot dry skin. Rapid and strong pulse. Possible unconsciousness.	Heat stroke is a severe medical emergency. Summon emergency medical assistance or get the victim to a hosiptal immediately. Delay can be fatal. Move the victim to a cooler environment. Reduce body temperature with cold bath or sponging. Use extreme caution. Remove clothing, use fans and air conditioners. If temperature rise again, repeat process. Do not give fluids.

Safety Tips

Slow down. Strenuous activities should be reduced, eliminated, or rescheduled to the coolest time of the day. Individuals at risk should stay in the coolest available place, not necessarily indoors.
Dress for summer. Lightweight, light-colored clothing reflects heat and sunlight, and helps your body maintain normal temperatures.
Foods (like proteins) that increase metabolic heat production also increase water loss.
Drink plenty of water or non-alcoholic fluids. Your body needs water to keep cool. Drink plenty of fluids even if you don't feel thirsty.
Do not drink alcoholic beverages.
Spend more time in air-conditioned places. Air conditioning in homes and other buildings markedly reduces danger from the heat. If you cannot afford an air conditioner, spending some time each day (during hot weather) in an air conditioned environment affords some protection.
Don't get too much sun. Sunburn makes the job of heat dissipation that much more difficult.

Air Temperature
F	C
Dew Point Temperature
F	C

Heat Index:
Relative Humidity: