The featured chart displays the daily difference in high and low temperature between the Des Moines ASOS and Ankeny AWOS weather station. Ankeny in a suburb of Des Moines and the sites are separated by only 12 miles. Recently, the daily low temperature has differed by up to 10 degrees Fahrenheit. The bottom chart shows that since June of 2012, Des Moines has almost always had a warmer overnight low temperature. It is not clear what could be causing this phenomena, but local micro-meteorological effects could certainly be at play here. It is somewhat disconcerting to see systematic shifts in this comparison that may be a sign of calibration or sensor issues. The Des Moines site is a part of the federal ASOS network, while the Ankeny site is an Iowa DOT AWOS site.

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