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!

It has been a very hot and humid start to September with high temperatures again soaring into the 80s and 90s for Iowa on Thursday. For Des Moines, the first three days of the month have had a high temperature of at least 95°F. The featured chart looks into the frequency of a given day of the year participating within a streak of at least as much days with such a warm high temperature. The earliest and latest streaks are listed off to the side. There have been later streaks into September on record, so this current one isn't exceptionally rare. The hot weather will continue into the Labor Day weekend with only slightly cooler weather expected next week, but still well above average.

While still humid, temperatures did cool off a bit on Sunday into Monday with a number of locations experiencing the first sub 70°F temperature reading of this September. For Des Moines, the low on Labor day was 67°F (hi kids), which was the coolest reading over the first seven days of September. The featured chart presents the coolest low temperature over the first seven days each year on record for Des Moines. Remarkably, four other years had experienced a warmer minimum over this period including 2015. Plenty of warm days are forecast for the shortened work week before perhaps cooler weather arrives for the following week.

It has been quite the year for big rainfall events over the Des Moines metro area. Last night's event brought severe thunderstorms to the metro area with intense rainfall rates leading to flash flooding. The featured map combines NOAA MRMS 24 hour precipitation estimates ending at 7 AM with NWS and CoCoRaHS reports. A stripe above five inches is shown across southern Polk County (Des Moines). Previous and similar IEM feature maps include 4 July and 21 July.

Yesterday's daily feature presented a 24 hour precipitation estimate with reports overlain over the Des Moines Metro showing a stripe of 5 to 6 inches over southern Polk County (Des Moines). One of the observation locations within that stripe was the Des Moines Airport. The weather station there recorded 3.77 inches on Tuesday (a daily record) and 2.12 inches on Wednesday making for a two day total of 5.89 inches. The featured chart presents the largest two day precipitation totals for Des Moines and shows the most recent event coming in fourth largest on record and the largest total since the 1970s.

With high temperatures on Friday expected to reach the lower 80s for much of Iowa and a handful of days over the coming week as warm, it is a good time to check in on the number of days per year with a high temperature of at least 80°F for Ames. The side tables list the top 10 years with the most and least number of days. The bars are colored by their departure from a simple period of record average (black line at 91 days). The 2026 total hasn't quite breached the top 10, but is already well above most years over the past two decades. It is also the seventh consecutive year above average.

A remarkably wet week of weather is forecast over the Midwestern US. The featured map presents Weather Prediction Center forecast precipitation over the next seven days ending Sunday evening. Most of Iowa is shown at three inches and higher accumulations over this period. The regions plotted in black are over seven inches for this period! This forecast "paints" precipitation with broad brush strokes, so locally much higher amounts are anticipated over more isolated locations. This week will certainly put the breaks on any fall season harvest progress as it appears no locations within Iowa will avoid significant rainfall.