The last day of August was quite hot with high temperatures in the upper 80s and 90s with dew points well into the 70s for Iowa. Summer is certainly not ending with the calendar now turned into September with a number of hot days yet to go. Having high temperatures around 90 degrees for the first of September is nothing too out of the ordinary and in fact, is about the average last date of the year for such a temperature. While the featured chart looks like a funnel, it isn't necessarily a "funnel plot" as the feature title suggests. The plot shows the period each cold season between the average last and first day of the calendar year at a given high temperature for Ames. The chart nicely shows a general rule of thumb for fall Iowa with with the last 90 around 1 September, the last 80 around 1 October, and the last 70 around 1 November. This chart can be kind of depressing if you like the warm temperatures as it shows how long it takes for them to return during the spring season!

The first day of September felt nothing like fall with near record high temperatures and very humid air. For Sioux City, the maximum reported dew point temperature based on hourly reports was 77°F, which was an unofficial record maximum for the month of September. Yes yes, setting such a record on the first day of the month somewhat diminishes the record as it would not be a record during August. That issue aside, the featured chart presents the hourly maximum dew point reports for the site during the month of September. Dew point readings on Monday were buoyed over northern Iowa thanks to "moisture pooling" along a frontal boundary. Hot and marginally less humid conditions will continue today as summer rolls on!

Wednesday was another too-hot-for-September day with high temperatures well into the 80s and even 90s for most of Iowa. Scattered showers did develop over northern Iowa and provided a small respite from the hot temperatures. The featured chart presents one minute interval data from the ISU Soil Moisture station west of Ames and very close to the Farm Progress Show location near Boone. The chart plots air temperature, dew point, solar radiation, wind speed, wind gust, and precipitation. A number of interesting features can be seen during the afternoon hours. It got cloudy as shown by the reduced solar radiation, but only 0.02" of an inch of precipitation was reported during this time. Wind speeds slackened due to reduced solar heating and subsequent reduced vertical mixing down of higher momentum air. Dew point temperatures creeped up during this period as well, which is likely due to some evaporation of water drops before reaching the ground and decreased vertical mixing of transpired water by vegetation. At about 4 PM, sunshine returned and the processes reversed with increased winds, slightly lowered dew point due to vertical mixing and increasing air temperatures. By 6 PM, air temperatures returned to where they started at noon at 90°F. One minute charts are always fun to diagnose!