The calendar has mercifully turned to October and after the rains end this morning, there is hope for a much needed upcoming stretch of drier weather. Will likely be able to create a number of daily features over the coming days denoting how remarkable the weather of this past September was. The featured chart today looks into daily average relative humidity as computed for the Des Moines Airport weather station. The top panel plots the daily observations along with the climatology which has been smoothed to remove the day to day noise. The bottom panel plots the smoothed frequency of having the daily average relative humidity above 90%. Around 10 days for 2026 are shown having an average relative humidity of 90% or greater, which works out to 33% of the days! The bottom panel puts the climatology around 5% of the days. High humidity and the lack of a killing frost are contributing to significant grain quality concerns as a mature crop continues to wait to be harvested.

It would appear that the recent non-stop rainfall events have finally relented with dry weather lasting into next week along with plenty of sunshine currently forecast. The lack of dry weather during September has certainly delayed the fall harvest season for Iowa. The featured chart presents USDA NASS soybean harvest estimates for Iowa. The NASS reports are weekly, so daily values are linearly interpolated between the weekly reports. The most recent report valid on this past Sunday estimated just 3% of Iowa's soybean acres as harvested. The left hand chart plots the yearly process numbers with the 3% value denoted each year. The right hand chart lists out those yearly 3% dates. Only a couple of years over the past 15-20 have been more delayed than this year. Things will likely not have improved much when NASS releases its next report on Monday as significant rains fell this week and we will need a number of days to dry out!