The start of a new month is always a good time to review what happened for the previous month. The featured chart reviews hourly aviation flight rules computed from the Des Moines airport weather station. These rules consider cloud ceilings and horizontal visibility among other things to restrict aviation traffic. The featured chart only considers the weather station horizontal visibility distance and vertical distance to cloud coverage either in "broken" or "overcast" state. The chart is a nice first guess to indicate periods where there was likely poor flying weather conditions due to visibility reductions. The stormy start to April is most noticeable with reductions more isolated after the first few days.