Storms developed along a frontal boundary over southwestern Iowa on Monday afternoon with muggy air ahead of the front helping to fuel the storms. Cooler and less humid air has worked into the state overnight with dew point temperatures 10 to 15 degrees cooler. The featured chart looks into six hour dew point temperature change based on hourly data from the Des Moines airport. The data is partitioned by one degree Fahrenheit and by week of the year with the frequency units being average number of hours per week per year. Certainly values near zero are the most common as dew point fluctuations are less than air temperature. It is interesting to denote the largest frequencies at values just above zero during late June into late August. Some of this is the effect of evapo-transpiration processes adding moisture to the air during daytime hours, but it is also a tightening of the possible distribution of dew point temperatures during the most humid time of the year.