Marshalltown dipped to 50 degrees Tuesday morning for the first time since 1 July. The featured chart presents the first date of a sub 51 degree temperature for the site for each year on record. The number of subsequent days afterward is then plotted to the first sub 32 degree temperature each year. The slanted dashed lines provide a reference back to the abscissa allowing for the date of the first sub 32 to be determined. A simple linear trend line is fit as well and the less than -1 slope is interesting as it likely indicates that the deeper you go into the fall season to have your first 50 degree low temperature the relatively longer it will take to get the first sub 32 degree value. Anyway, there is lots of spread to the chart as values in early August range from 50 to 90 days, so not very predictive to the first fall freezing temperature.

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