Weather: Higher heat index makes Northwest feel uncomfortable

In our part of the country, when temperatures soar into the 90s, humidity levels are often low. However, with increased humidity levels amid scattered shower and thunderstorm activity, it has felt more uncomfortable. This week’s pattern was more like one in the southern U.S.

Temperatures and humidity levels combine to produce a heat index. This table was developed in 1979 by R.I. Steadman of the National Weather Service and shows the reading of what the human body actually feels.

The heat index, which is most commonly used in warm and humid regions, is calculated by combining air temperature and relative humidity levels. For example, an air temperature of 85 degrees combined with a relative humidity reading of 80 percent results in a heat index of 97 degrees. At the airport on Monday, the heat index was near 100 degrees despite an air temperature around 90 degrees.

Excessive heat is dangerous to the human body, and prolonged exposure can be fatal.

During a normal year, the heat-index readings are far lower in the northern and western parts of the country, including the Inland Northwest. In our region, the warm, humid air from the Gulf of Mexico is blocked by the Rocky Mountains. This often leads to low humidity levels that are usually below 20 percent during very hot days. However, this week’s weather is a little different, as some moisture has been moving northward from the Southwest, which has been receiving flooding rains in recent weeks.

We still have plenty of summer weather ahead. One should use caution with heat-index temperatures above 90 degrees. It usually becomes “extremely dangerous” or deadly with heat-index levels above 125 degrees.