Wednesday, July 13, 2011

East Texas Heat Reaching Dangerous Levels

The song, "The Heat is On" by Glenn Frey would be fitting for our East Texas weather over the past couple of months. Only now, it is really on and has become more dangerous.

Our heat index or feels like temperatures this afternoon have gone over 105° and have been closer to 110° in many instances.

The heat index is determined by combining the actual air temperature with the relative humidity. Typically, during the afternoon, when the temperatures are in the low 100's, the relative humidity values are in the 20-30% range. When the highs only reach the lower to middle 90's, the relative humidity is much higher, say 50%. They have an inverse relationship and offset each other.

That's why sometimes residents in Arizona will tell you they have a dry heat. In some cases, a temperature of 102° may feel not as hot or oppressive as a temperature of 95°. Why would that be? Well, that's because the hotter temperature has the lower humidity value, therefore, it does not feel quite as humid and sauna-like.

A Heat Advisory remains in effect for Angelina, Nacogdoches counties, and all points north and east of there through Thursday evening. Unfortunately, those heat indices will be at dangerous levels again on Thursday.

The image above is a heat index chart. It plots the temperature on the horizontal axis vs. the humidity on the vertical axis. The value that comes together is the actual feels like value. You may want to refer to this so you can see just how hot it actually feels where you live.