Past Features
This page lists out the IEM Daily Features for a month at a time. Features have been posted on most days since February 2002. List all feature titles.
Fri Aug 01, 2025
July 2025 vs 1993
01 Aug 2025 05:30 AM
The month of July has mercifully come to a close with the stormy and muggy weather replaced by comfortable temperatures, but poor air quality. The featured chart presents a smoothed analysis of total precipitation differences between July 1993 and July 2025 for long term climate sites having data for both years. While there was some flooding this July, it certainly wasn't to the scale of what happened during 1993. The next few daily features will try to show why the situation was different. So the featured map today subtracts the 1993 total from 2025, so a negative (red shading) value would indicate the 1993 total was larger than 2025. So while some parts of the state had more precipitation during 2025, there are some some very large differences in the other direction. You can generate this same map to compare the two years for June and you will find a similar story and most relevant for Des Moines 1993 flooding, much less precipitation over the river basins north of Des Moines than during June 1993.
Voting: Good - 13 Bad - 1
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01 Aug 2025 05:30 AM
The month of July has mercifully come to a close with the stormy and muggy weather replaced by comfortable temperatures, but poor air quality. The featured chart presents a smoothed analysis of total precipitation differences between July 1993 and July 2025 for long term climate sites having data for both years. While there was some flooding this July, it certainly wasn't to the scale of what happened during 1993. The next few daily features will try to show why the situation was different. So the featured map today subtracts the 1993 total from 2025, so a negative (red shading) value would indicate the 1993 total was larger than 2025. So while some parts of the state had more precipitation during 2025, there are some some very large differences in the other direction. You can generate this same map to compare the two years for June and you will find a similar story and most relevant for Des Moines 1993 flooding, much less precipitation over the river basins north of Des Moines than during June 1993.
Voting: Good - 13 Bad - 1
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Mon Aug 04, 2025
2025 vs 1993 Soil Moisture
04 Aug 2025 05:30 AM
The past few IEM Daily Features have been looking into differences between July 1993 and 2025. July of both years had tremendous amounts of rain for Iowa, but the resulting flooding was much different. Today's featured chart likely best explains why. The chart uses a grid point sample of one meter depth soil moisture estimates from the ERA5-Land reanalysis. This plotted grid point sample is for Boone, which is upstream from Des Moines. The period of record range is plotted along with some simple statistical measures. Of most relevance are the yearly values for 2025 (black line) and 1993 (blue line). Soil moisture values during 1993 were much above 2025, which implies more runoff during 1993 as the soil had reduced capacity. The saturated condition of the soil during July 1993 is noticeable as well, with values at the top end of the observed range.
Voting: Good - 9 Bad - 0
Tags: jul1993 jul2025
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04 Aug 2025 05:30 AM
The past few IEM Daily Features have been looking into differences between July 1993 and 2025. July of both years had tremendous amounts of rain for Iowa, but the resulting flooding was much different. Today's featured chart likely best explains why. The chart uses a grid point sample of one meter depth soil moisture estimates from the ERA5-Land reanalysis. This plotted grid point sample is for Boone, which is upstream from Des Moines. The period of record range is plotted along with some simple statistical measures. Of most relevance are the yearly values for 2025 (black line) and 1993 (blue line). Soil moisture values during 1993 were much above 2025, which implies more runoff during 1993 as the soil had reduced capacity. The saturated condition of the soil during July 1993 is noticeable as well, with values at the top end of the observed range.
Voting: Good - 9 Bad - 0
Tags: jul1993 jul2025
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Tue Aug 05, 2025
Reaching 2400 GDDs
05 Aug 2025 05:30 AM
With the calendar now firmly within August, the fall season is not all that far away! This is about the time of year when fretting occurs for if enough heat units will be accumulated to bring crops to maturity prior to the first fall freeze. The featured chart is one such tool in this space and presents frequencies of reaching 2,400 growing degree days by the given fall date for a given start date (read planting date) for Ames. The left hand chart shows climatological values using period of record observations and the right hand chart presents probabilities using the current 2025 accumulation to 4 August and then appending all previous years onto the current year to create possible scenarios. While 2,400 units is an aggressive maturity number for Ames given the frequency drop off with late May planting dates shown by the left hand plot, this year looks in rather good shape with even late May planting dates needing to make it into the third week of September to reach maturity. Of course, things aren't generally this simple for a crop reaching maturity and the freezing date cut-off of only breaching 32 degrees is likely too restrictive as well, but the plot tells an informative story.
Voting: Good - 8 Bad - 0
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05 Aug 2025 05:30 AM
With the calendar now firmly within August, the fall season is not all that far away! This is about the time of year when fretting occurs for if enough heat units will be accumulated to bring crops to maturity prior to the first fall freeze. The featured chart is one such tool in this space and presents frequencies of reaching 2,400 growing degree days by the given fall date for a given start date (read planting date) for Ames. The left hand chart shows climatological values using period of record observations and the right hand chart presents probabilities using the current 2025 accumulation to 4 August and then appending all previous years onto the current year to create possible scenarios. While 2,400 units is an aggressive maturity number for Ames given the frequency drop off with late May planting dates shown by the left hand plot, this year looks in rather good shape with even late May planting dates needing to make it into the third week of September to reach maturity. Of course, things aren't generally this simple for a crop reaching maturity and the freezing date cut-off of only breaching 32 degrees is likely too restrictive as well, but the plot tells an informative story.
Voting: Good - 8 Bad - 0
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Wed Aug 06, 2025
Waterloo Warmer than Des Moines
06 Aug 2025 05:30 AM
While only by one degree (83° vs 82°), the Waterloo airport reported a warmer high temperature than Des Moines on Tuesday. The frequency of this happening is the subject of today's daily feature. The chart presents the daily frequency of the Waterloo high temperature being at least one degree warmer than Des Moines. A rather clean annual signal is shown with the highest frequencies happening during the late spring/early summer and the lowest frequencies during winter. The winter difference likely has to do with larger snow cover frequencies for Waterloo vs Des Moines. The peak in May likely has to do with local land use and soil differences, which leads to more efficient heating rates at Waterloo. The values though are practically all below 50% and the overall average is near 25%, so this micro-climate difference isn't enough to make Waterloo a warmer climate than Des Moines.
Voting: Good - 8 Bad - 1
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06 Aug 2025 05:30 AM
While only by one degree (83° vs 82°), the Waterloo airport reported a warmer high temperature than Des Moines on Tuesday. The frequency of this happening is the subject of today's daily feature. The chart presents the daily frequency of the Waterloo high temperature being at least one degree warmer than Des Moines. A rather clean annual signal is shown with the highest frequencies happening during the late spring/early summer and the lowest frequencies during winter. The winter difference likely has to do with larger snow cover frequencies for Waterloo vs Des Moines. The peak in May likely has to do with local land use and soil differences, which leads to more efficient heating rates at Waterloo. The values though are practically all below 50% and the overall average is near 25%, so this micro-climate difference isn't enough to make Waterloo a warmer climate than Des Moines.
Voting: Good - 8 Bad - 1
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Thu Aug 07, 2025
Solar Radiation Departures
07 Aug 2025 05:30 AM
A few recent requests to the IEM have wondered about solar radiation departures. These values are difficult to come by due to lack of observations, lack of robust climatologies, and general familiarity / applicability with what the values even mean. One approach is to use a model with near real-time estimates and a long term archive to attempt such a departure calculation. The IEM merges a couple of model estimates of solar radiation with the standard COOP daily observations to provide a downloadable dataset. The featured image looks into the NASA POWER estimates for Ames with 2025 daily values compared with period of record estimates back to 1984. A daily departure is plotted on the top panel and an accumulated departure is plotted within the bottom panel. This estimates a net positive ~50 Megajoules (MJ) departure since 1 May. One way to contextualize that value is that a sunny day this time of year should yield at least 25 MJ, so that departure would indicate a bonus of two extra sunny days vs an average accumulation. One item to note is that there are data availability lags with datasets like NASA POWER, so the plot indicates data only available up till 2 August.
Voting: Good - 8 Bad - 0
Tags: solarrad
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07 Aug 2025 05:30 AM
A few recent requests to the IEM have wondered about solar radiation departures. These values are difficult to come by due to lack of observations, lack of robust climatologies, and general familiarity / applicability with what the values even mean. One approach is to use a model with near real-time estimates and a long term archive to attempt such a departure calculation. The IEM merges a couple of model estimates of solar radiation with the standard COOP daily observations to provide a downloadable dataset. The featured image looks into the NASA POWER estimates for Ames with 2025 daily values compared with period of record estimates back to 1984. A daily departure is plotted on the top panel and an accumulated departure is plotted within the bottom panel. This estimates a net positive ~50 Megajoules (MJ) departure since 1 May. One way to contextualize that value is that a sunny day this time of year should yield at least 25 MJ, so that departure would indicate a bonus of two extra sunny days vs an average accumulation. One item to note is that there are data availability lags with datasets like NASA POWER, so the plot indicates data only available up till 2 August.
Voting: Good - 8 Bad - 0
Tags: solarrad
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Fri Aug 08, 2025
Centerville Heavy Rainfall
08 Aug 2025 05:30 AM
After a bit of a respite to start August, we are back to where July left off with isolated and near daily heavy rainfall events. On Thursday morning, a training complex of storms dumped heavy rainfall from Des Moines southward to Centerville. The featured map presents a smoothed analysis of available NWS Local Storm Reports, COOP, and CoCoRaHS rainfall totals valid Thursday morning. The 7.3 inch report plotted on the map is near Centerville. The autoplot that generated this map was recently updated to support these rainfall reports. It previously was the app that generated snowfall analysis maps in a similar form.
Voting: Good - 16 Bad - 0
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08 Aug 2025 05:30 AM
After a bit of a respite to start August, we are back to where July left off with isolated and near daily heavy rainfall events. On Thursday morning, a training complex of storms dumped heavy rainfall from Des Moines southward to Centerville. The featured map presents a smoothed analysis of available NWS Local Storm Reports, COOP, and CoCoRaHS rainfall totals valid Thursday morning. The 7.3 inch report plotted on the map is near Centerville. The autoplot that generated this map was recently updated to support these rainfall reports. It previously was the app that generated snowfall analysis maps in a similar form.
Voting: Good - 16 Bad - 0
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Mon Aug 11, 2025
Top 10 Rainfall for Dubuque
11 Aug 2025 05:30 AM
The near daily deluges of rainfall impacting somewhere in Iowa continued over this past weekend. The Dubuque airport was the deluge recipient on Sunday with a daily total near five inches, which is a top 10 rainfall on record for the site. The featured chart presents the top 10 daily rainfall events for the long term data from Dubuque, which dates back to 1873! The 2011 event was covered by an IEM Daily Feature showing the one minute interval precipitation. The data for this event won't fully come in until Monday evening. While there is more chances of rain in the forecast this week, it does look more dry than wet, which would be good news for most Iowans and for Iowans wishing for fair Iowa State Fair weather!
Voting: Good - 9 Bad - 1
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11 Aug 2025 05:30 AM
The near daily deluges of rainfall impacting somewhere in Iowa continued over this past weekend. The Dubuque airport was the deluge recipient on Sunday with a daily total near five inches, which is a top 10 rainfall on record for the site. The featured chart presents the top 10 daily rainfall events for the long term data from Dubuque, which dates back to 1873! The 2011 event was covered by an IEM Daily Feature showing the one minute interval precipitation. The data for this event won't fully come in until Monday evening. While there is more chances of rain in the forecast this week, it does look more dry than wet, which would be good news for most Iowans and for Iowans wishing for fair Iowa State Fair weather!
Voting: Good - 9 Bad - 1
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Tue Aug 12, 2025
Empty Bucket Days
12 Aug 2025 05:30 AM
For all of the complex, non-linear, and compute intensive models that exist within meteorology/climatology, sometimes the simplest can be quite illustrative. Such is the case for the "leaky bucket model". The concept is simple, you have a bucket with a given depth (capacity) for water (filled by precipitation events) that leaks at some daily rate (evaporation, infiltration, runoff, etc). The two constraints are that the bucket can not be filled beyond its capacity and an empty bucket can not leak. The featured chart presents the data for Ames (picking a 1.5 inch bucket depth and 0.15 inch daily leak rate) between 1 May and 11 August for this year (top panel) and then the count of days each year for this period with an empty bucket. The chart nicely shows that this theoretical bucket has not been empty since mid June, but was for a number of such days prior to then so while the 2025 total is well below a simple average, it is still a number of days higher than 2024! You can tweak this model as you wish by following the "Generate this Chart" link.
Voting: Good - 9 Bad - 0
Generate This Chart on Website
12 Aug 2025 05:30 AM
For all of the complex, non-linear, and compute intensive models that exist within meteorology/climatology, sometimes the simplest can be quite illustrative. Such is the case for the "leaky bucket model". The concept is simple, you have a bucket with a given depth (capacity) for water (filled by precipitation events) that leaks at some daily rate (evaporation, infiltration, runoff, etc). The two constraints are that the bucket can not be filled beyond its capacity and an empty bucket can not leak. The featured chart presents the data for Ames (picking a 1.5 inch bucket depth and 0.15 inch daily leak rate) between 1 May and 11 August for this year (top panel) and then the count of days each year for this period with an empty bucket. The chart nicely shows that this theoretical bucket has not been empty since mid June, but was for a number of such days prior to then so while the 2025 total is well below a simple average, it is still a number of days higher than 2024! You can tweak this model as you wish by following the "Generate this Chart" link.
Voting: Good - 9 Bad - 0
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Wed Aug 13, 2025
First Fall Low Temp Dates
13 Aug 2025 05:30 AM
The official low temperature for Des Moines has yet to breach 60°F since the first of July. The featured chart presents accumulated frequencies of having the first fall season (after 1 July) temperature below the given threshold by the given date of the year. For August 12th and 60 degrees, the frequency is about 80%, so about four out of every five years have seen such a cool temperature by the current date. The chart also shows three other thresholds for comparison. Frequencies of the first sub 50 really start to increase by the end of next week, but the 50 percent value does not come until September. The urban heat island of Des Moines certainly helps to buoy overnight temperatures as sub-60 values will be common this week outside of city including those this Wednesday morning.
Voting: Good - 8 Bad - 0
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13 Aug 2025 05:30 AM
The official low temperature for Des Moines has yet to breach 60°F since the first of July. The featured chart presents accumulated frequencies of having the first fall season (after 1 July) temperature below the given threshold by the given date of the year. For August 12th and 60 degrees, the frequency is about 80%, so about four out of every five years have seen such a cool temperature by the current date. The chart also shows three other thresholds for comparison. Frequencies of the first sub 50 really start to increase by the end of next week, but the 50 percent value does not come until September. The urban heat island of Des Moines certainly helps to buoy overnight temperatures as sub-60 values will be common this week outside of city including those this Wednesday morning.
Voting: Good - 8 Bad - 0
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Thu Aug 14, 2025
Backing Off Humidity
14 Aug 2025 05:30 AM
Humidity levels have felt a bit nicer to start off this week as the very muggy conditions last week have backed off some. The featured chart presents IEM computed daily max and min dew point temperatures along with a crude and smoothed period of record climatology for Estherville (NW Iowa). The climatology doesn't show much for a downward trend as the month of August progresses as more fall like weather (read lower dew points) typically waits till the second week of September or so to start showing up. A couple of days last week are shown having low dew point values near an average high value. Unfortunately, heat and humidity are building back into the state with a hot and muggy weekend forecast with air temperatures into the 90s and dew points in the upper 70s.
Voting: Good - 5 Bad - 0
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14 Aug 2025 05:30 AM
Humidity levels have felt a bit nicer to start off this week as the very muggy conditions last week have backed off some. The featured chart presents IEM computed daily max and min dew point temperatures along with a crude and smoothed period of record climatology for Estherville (NW Iowa). The climatology doesn't show much for a downward trend as the month of August progresses as more fall like weather (read lower dew points) typically waits till the second week of September or so to start showing up. A couple of days last week are shown having low dew point values near an average high value. Unfortunately, heat and humidity are building back into the state with a hot and muggy weekend forecast with air temperatures into the 90s and dew points in the upper 70s.
Voting: Good - 5 Bad - 0
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Fri Aug 15, 2025
Setting Records
15 Aug 2025 05:30 AM
The daily feature to start off this week highlighted a top 10 daily rainfall for Dubuque on Sunday, which was also a daily record for the site. The featured chart total follows up on this by plotting the number of newly set daily records by year for the site. The top panel shows maximum high temperatures, middle panel shows minimum low temperatures, and the bottom panel shows precipitation records. The line on each plot is a simple 365 divided by the number of years on record to represent an estimate of the number of new records possible that year. The color of the bars differentiate years above or below this 365/n line. The nicely nicely shows a common problem with long term climate site, in that they often move and this move can put them in a significantly different micro-climate. For Dubuque, prior to the early 1950s, the site was along the Mississippi River in the valley and afterwards moved to the airport up on the bluffs and away from the river! You can easily see the dramatic increase in low temperature records being set and limited new high temperatures.
Voting: Good - 10 Bad - 0
Tags: records
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15 Aug 2025 05:30 AM
The daily feature to start off this week highlighted a top 10 daily rainfall for Dubuque on Sunday, which was also a daily record for the site. The featured chart total follows up on this by plotting the number of newly set daily records by year for the site. The top panel shows maximum high temperatures, middle panel shows minimum low temperatures, and the bottom panel shows precipitation records. The line on each plot is a simple 365 divided by the number of years on record to represent an estimate of the number of new records possible that year. The color of the bars differentiate years above or below this 365/n line. The nicely nicely shows a common problem with long term climate site, in that they often move and this move can put them in a significantly different micro-climate. For Dubuque, prior to the early 1950s, the site was along the Mississippi River in the valley and afterwards moved to the airport up on the bluffs and away from the river! You can easily see the dramatic increase in low temperature records being set and limited new high temperatures.
Voting: Good - 10 Bad - 0
Tags: records
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