While the calendar now says October, the summer like temperatures look to continue through at least this upcoming weekend. The dry weather looks to continue as well. With the start of a new month, it is a good time to check in on September precipitation totals. The featured map presents a heavily smoothed analysis of available NWS long term climate site precipitation totals for September. Some rather paltry totals below an inch are found over far eastern and northwestern Iowa. The worsening drought this fall season continues to be of concern as the dry August for parts of Iowa was followed by even drier weather during September for most of the state. Not everybody missed out during the month with a number of locations plotted shown above 3.5 inches, which is about average for Iowa during September.
The very warm early fall season weather continued on the first day of October with highs reaching 80°F degrees for much of the state. The featured chart presents the daily frequency of such a warm high temperature by day of October for Ames. It is quite interesting to see the increased frequencies during the first few days and then the rapid drop off with a settling around 15% on October 5th. A climate explanation for this is not apparent! Of course, the overall trend is downward for the month with such days becoming more fleeting as we progress. Interestingly and coincidentally, the present forecast has temperatures dropping back near 70°F for highs on the 6th!
The National Weather Service produces a number of weather forecast products. One of those is called Model Output Statistics (MOS), which attempts to provide a bias-corrected and point specific forecast based on raw model output. The IEM processes the MOS text bulletins and offers some tooling for this data along with a download option. The featured chart is another tool in this space and plots the combination of morning low and afternoon high observations (dots) along with the time-lagged ensemble range of forecast values for the Ames Airport. In this case, the "GFS Extended" MOS product is plotted. The forecast trend is rather clear with cooler weather arriving to start off next week and lows even perhaps dipping into the 30s by later in the week. Could we perhaps finally be done with summer like heat?
The first five days of October were exceptionally warm with highs mostly in the 80s and lows in the 60s for Iowa. The featured chart presents the average temperature for the first five days of October for each year on record for Des Moines. The 2025 average near 75°F is almost 2 degrees warmer than the previous warmest value way back during 1900! A bit of fall reality has settled over Iowa for Monday, but far southeastern Iowa will have another day of very warm October temperatures. Even after this early week drop in temperatures, moderation will happen for the remainder of the weekend with forecast highs expected again to be near 80°F next weekend!
The featured map presents the combination of NOAA MRMS precipitation estimates from Sunday through early Tuesday morning and the current US Drought Monitor analysis. This needed precipitation event was thanks to a slow moving front that has swept the state clean of the very warm air that started off October. The map shows that much of the heaviest totals missed the parts of the state presently within a "D0" drought analysis, but the entire state needed rain. Once the showers clear southeastern Iowa later this morning, there are a few chances of light rainfall over the coming days along with warming temperatures.
The featured chart presents daily high and low temperature climatology for Ames along with 2025 observations. A lot of information is packed into one chart here with the range between the average high and low temperature shaded in green and then the area between those averages and the daily record maximum and minimum values shaded in red and blue respectively. The brown bars are the range between the 2025 daily high and low temperatures. Qualitatively, you can see we have spent very little time this warm season with low temperatures within the blue area (below average). The two cool periods of late August and early September are about all to speak of for such periods since early April.
For the month of September, the Storm Lake (NW Iowa) NWS COOP station reported just two daily rainfalls with 0.04" on the 10th and 0.42" on the 19th. So roughly 90% of the monthly total fell on just one day. The featured chart looks into the frequency of that happening with the most recent yearly occurrence shown above each bar. While generally rare, these events are most frequent during the colder half of the year when precipitation totals are lower and more easily comprised of just one big event. This situation is much more difficult during the summer months as rainfall events are more frequent and heavy rainfall events less isolated.
Daily high temperatures have steadily warmed this week with even warmer temperatures expected for the weekend. There's an outside chance that Ames could hit 80°F on Sunday, which would be the sixth such day this October. The featured chart looks into the monthly frequencies and percentiles of a daily high temperature of at least 80°F for Ames. The long term average number of such days during October is around three, so this year has already bested that average by two days. If you like such weather, you should certainly savor it as meaningful frequencies of such days does not return until next April!
