With the calendar now turned into August, we have fully reached the last half of the warmest part of the year. Average high temperatures have been slightly above average for the June through July period. The featured chart looks into if this portends what may happen during the August through September period. The chart presents the yearly combination of average high temperature for Ames for the sixty days prior to and after 1 August. Of note for this plot are the quadrant frequencies, which indicate a persistence to having both periods either below average or above average each year.

Agronomy Hall at Iowa State University hosts a PurpleAir air quality sensor. Unfortunately, wild fires and the associated smoke continues to be a problem plaguing much of the country. The featured chart presents the daily range of PM2.5 (2.5 micrometers or less) Air Quality Index (AQI) for 2026. The chart colors represent the ranges of values associated with the given AQI rating. The wild fire smoke has certainly been noticeable over Iowa these past number of weeks. The hazardous levels were reached just over a week ago on 24 July.

In the category of life imitating art, yesterday (4 August 2026) was the future date referenced in the 1950 short story "There Will Come Soft Rains" written by Ray Bradbury. While some Iowans did experience something more than soft rains, a majority of the state received something much softer. The featured chart presents one minute interval data from the ISU Soil Moisture station just west of Ames. The bottom panel shows the one minute interval rainfall totals. The station utilizes a classic tipping bucket to report rainfall in 0.01 inch increments (one tip of the automated mechanism). So the minute totals are not a true minute accumulation as the time to generate one tip can take more than one minute. The label above the plot provides the maximum rainfall accumulations over various intervals of time. Those maximum values are not excessive at all and likely quality as a "soft rain" for most folks!

For the first week of August, Wednesday was a very cool day with a number of locations unable to reach a high temperature of 70°F. One such location was Waterloo with a high of just 69°F. The featured chart looks into the accumulated frequency by fall season date for the first sub threshold daily high temperature. The algorithm considers any post 1 July date as the "fall season", but starts the plot on 1 August. For the sub 70°F threshold, yesterday's value comes in around the 10th percentile. Rewording, about one in ten years have seen such a cool high by the 5th of August. Some selected lower thresholds are plotted as well with sub 65°F having a much lower accumulated frequency until about the last week of August. We are still squarely within the summer season for Iowa, so these respites from the heat should be enjoyed!

One of the most frequently issued National Weather Service headlines is the ever exciting Dense Fog Advisory. A number of such advisories have been issued over Iowa this week as a cooler air mass has interacted with late summer elevated humidity. The featured chart looks into the frequency of such advisories issued by NWS Des Moines by time of day. The chart presents the summer season (June, July, August) frequency along with the overall full year frequency. The difference between the two is quite informative. During the summer season, solar inputs are very strong and will work to "burn off" the fog pretty much every day. Of course, there is no "burning" process, but a process of heating the ground, heating the lower atmosphere and reducing relative humidity levels. Such is the case again this Friday with morning fog and a number of advisories currently active.

Severe storms impacted eastern Iowa Friday afternoon producing an EF2 Tornado near Fairbank and damaging winds elsewhere. When the National Weather Services issues Severe Thunderstorm and Tornado Warnings for such storms, the warnings contain an estimate of storm speed and direction of travel. The featured chart presents such storm motion estimates from NWS Davenport during the summer months of June, July, and August (JJA). The warnings from Friday are highlighted with the red crosses. The blue lines attempt to show where the most frequent combinations of storm speed and motion reside. The bullseye appears to be somewhere near a storm motion from the west around 40 MPH. You can generate this chart for other months of the year and compare how the storm motion changes during the year.

Atmospheric soundings are an important observational dataset useful for the forecasting the weather. The often twice-daily balloon launches by the National Weather Service capture vertical profiles of temperature, humidity, pressure, and wind. These profiles can be used to compute many useful indices to access the state of the troposphere. Once such index is Convective Available Potential Energy (CAPE), which is useful for understanding how much potential energy is available for near surface air if it were to be lifted vertically and become buoyant. The CAPE index is not necessarily easy to compute and subject to many interpretations and assumptions. The featured chart presents the CAPE index for surface based "parcels" based on soundings from NWS Davenport. The balloon launch Monday evening (00 UTC 11 August 2026) captured a very unstable environment with a CAPE index around 7,700 J/kg. Based on unofficial archives, this was the largest CAPE value for August and one of the largest on record for the site. Large CAPE values are often associated with a "cap" of warm air aloft that prevents storm development, so these environments do not automatically produce severe storms. Generally speaking, CAPE is not a lifting mechanism but an energy reservoir available to support explosive development should air be lifted to levels were it can "freely convect".

For the National Weather Service office at Davenport (Quad Cities), it has been a very active year for severe weather. Severe storms once again visited eastern Iowa early Tuesday morning with three EF-1 tornadoes surveyed over Delaware County. Based on unofficial IEM archives, the featured chart presents the number of year to date Tornado Warnings issued by the office since 1986. The 2026 total of 86 warnings easily surpasses any previous year. Unfortunately, more chances of severe weather are in the forecast for much of the remainder of this week.