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Why did my forecast change?

The wet bulb globe temperature (WBGT) forecasts are calculated from National Weather Service (NWS) forecasts of temperature, humidity, sky cover, and wind speed.  These forecasts often change slightly in response to new information produced by the latest weather models.

Why do I get different measurements at different locations?

WBGT accounts for temperature, humidity, sunlight, and wind speed, each of which can change from one location to another; consequently, the WBGT measurement can change as well.  For example, the humidity of the air near a lake or water source is usually higher than that over a dry open field, thus WBGT will be higher.  Because of these local variations, it is important to take WBGT measurements at the actual location of planned activities.

Where is the best location to take my WBGT measurement?

The best location to take the WBGT measurement is the location(s) in which the activity will occur.  Since WBGT accounts for four meteorological variables (e.g. see above), different surfaces (e.g. grass field versus a tennis court) often have different WBGT values.  Therefore, it is important to realize a WBGT value is specific to the place you are taking the measurement.

How does WBGT differ from Heat Index?

Like the heat index, the WBGT takes into account the temperature and humidity of the air.  It also considers the effects of solar radiation (e.g. heat stress is greater in the sun) and the wind speed (e.g. heat stress much greater when the winds are not blowing).