Based on hourly grid analyses of near surface air temperature by NCEP RTMA, the featured map presents the longest consecutive hour streak with the temperature below 0 Fahrenheit. Maps like these often tease out interesting land form regions of the state as such things like topography and land use help inform the analysis procedure. The sharp differences in the plot are due to a brief warmup on Sunday that brought parts of the state briefly above zero and thus split the extended period below zero into two parts. According to this analysis, a section of Osceola County in far NW Iowa had the longest stretch lasting over six days (144 hours). Thankfully our future periods below zero are expected to brief and confined to overnight hours.

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