This week has a warm and muggy one with heat indices pushing 100 degrees in some locations. The popular phrase, "it isn't the heat, its the humidity", means that warm temperatures are bearable unless high levels of humidity exist at the same time. The featured chart presents the frequency of having either a 3+ or 5+ difference between the temperature and heat index when the air temperature is at or above 80 degrees. This "humidity effect" indicates how often the humidity levels are high enough to produce a noticeable difference from the temperature. Long term averages are shown for each value with bars above or below average colored separately. For Des Moines, about 50% of the time when temperatures are above 80 the heat index is adding at least three degrees to the temperature. The average is just below 30% for a five degree change.

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Tags:   heatindex