The Heat Index has not been a prominent topic so far this summer as temperatures have been cool and the warm days have mostly seen limited humidity levels. The featured chart attempts to provide a climatology for heat index for Des Moines. The contours on the plot are the temperature difference the heat index is from the air temperature. For example, at 90 degrees and 50% relative humidity the heat index adds two degrees to the temperature. The color pixel values are the relative frequency of the given relative humidity at the given temperature, meaning that each column has a sum of 100%. The point of the plot is to show the most common combinations of temperature and relative humidity along with the heat index that produces. Thankfully, as the temperature increases the relative humidity tends to decrease which limits the heat index (the water content of the air does not change only the water holding capacity). The chart also indicates that the heat index is rarely adding over 14 degrees to the temperature and typically something less than 6 degrees. The forecast has some of the warmest heat index values of the year so far set to arrive this weekend.

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Tags:   heatindex