May was a recording setting month for precipitation over much of the plains. While Oklahoma and Texas got most of the headlines due to the devastating flooding, heavy rains also fell further north all the way to the Canadian border. The featured map displays IEM computed precipitation percentiles for May by climate district. Plotted values of 1 would indicate the wettest May on record (since 1893) for the area. Only the eastern portion of the Midwest is shown to have had a dry May.

The weather for the first day of June was a real trick with temperatures in the 70s, low humidities and sunny skies. If you are a fan of having mid afternoon temperatures in the 70s, then June is your month as shown by the featured chart. The chart presents the frequency of having the 3 PM (CDT) [2 PM LST] temperature in the 70s for Ames. June has the highest frequency. The frequency dips in July as temperatures are often warmer than the 70s.

The featured chart displays the high and low temperature distributions for 2 June from long term reporting sites in Iowa. The actual reports on Tuesday were about in the middle of the long term distributions. It is interesting to compare the shapes of the two curves. The low temperature distribution is narrower due to the different processes that govern the daily low temperature versus the high. The low temperature is typically a function of overnight clouds, soil temperatures, and humidity levels, while the high temperature is related to amount of sunshine and air mass transport.

While an IEM feature a few weeks back showed that the maximum reported dew point for the year to date was one of the lowest in recent years, the actual average dew point continues the recent trend of above long term average value. The featured chart displays an IEM computed average dew point reading for the Des Moines Airport for the spring season of March, April and May since 1970. The trend line for this period is upward with 13 of the past 18 years above the long term average.

Yesterday's feature presented the average spring season dew point and showed an increasing trend. Similarly, today's plot shows yearly spring season precipitation totals averaged over the state of Iowa and again, an increasing trend is shown. The right most bar on the plot would be this years total and it is slightly above long term average as well.

Some much needed rainfall fell over Iowa on Sunday with a round of heavy showers in the morning and then again in the late afternoon. The featured map looks at one of the intense stripes of rainfall over just four counties in central Iowa. The colors are estimates from NOAA MRMS Q3 and the plotted values are 24 hour precipitation reports from the NWS COOP network. Your location in these four counties made a big difference to the amount of precipitation you received. Just over Webster County, you can see the reports ranged from 3 tenths to 2.3 inches!

Warm weather has been difficult to come by so far this growing season and with often chilly overnight lows, the growing degree day accumulation is running behind average. The featured chart shows the accumulation for Ames since 1 May. The dashed line in the bottom chart shows the to date departure. Since mid May, we have been loosing ground. Today will be the warmest high temperatures we have seen this year, but rain and a bit cooler weather is in the forecast for the rest of the week.

The warmest day of the year by far was yesterday with high temperatures soaring into the 90s. This was the warmest weather we have seen since last September. The featured chart displays the period for Ames between the average last date for a high temperature at or above a given threshold to the average first date of the year. The right hand side chart is simply the number of days represented by the bars. The change in slope of the plot on the right hand side is interesting and it is not clear exactly what it is illustrating, but as you get to very warm temperatures, the annual influence on the period decreases as the average period increases to a full year's period.

Widespread and heavy rainfall events have been difficult to come by this year. Thanks to some extra atmospheric moisture provided by an old tropical system, that looks to change with our near term stretch of weather. Heavy rainfall has started overnight and will continue for the next few days. The featured map is a forecast of precipitation totals for the next five days from the Weather Prediction Center. Parts of northern Iowa are indicated to approach four inches of rain.

The ASOS weather stations in the state record precipitation at one minute intervals. With this data, the featured chart presents the highest rainfall accumulation over a given number of minutes. This chart is useful from an engineering perspective as various structures are designed to handle a certain amount of water over a certain amount of time. There are numerous caveats to this chart including the fact that automated sensors struggle to accurately record these intense rates and the ASOS station includes an upward adjustment when rainfall rates get this high to account for under-catch. Having said all that, the chart does nicely illustrate the duration of the most intense thunderstorms. Since we are not situated against a mountain, storms have to move to maintain a source of energy, so the most rates are generally done within 30 minutes or so. Having sequential thunderstorms of this intensity is not going to happen as the atmosphere can not 'refill' its supply of water that quickly without the help of a mountain. There are some differences between the five sites plotted, but the differences are likely due to sensor / siting differences and not a physical explanation (perhaps). There is also only 15 years of data comprising this chart, so the sample size is a bit small.

The featured map displays the combination of average first date per year of 90+ degree high temperatures and the locations that have seen such a temperature so far this year. Please note that the locations plotted with an "X" are thinned for readability. In general, this year lines up nicely with climatology as evaluated for mid June. Only portions of the eastern corn belt are shown as behind. The forecast for this week looks stormy with highs only reaching the low 80s.

The featured map displays NWS Local Storm Reports of accumulated rainfall from Sunday evening through Monday morning. The map is focused on the Des Moines Metro. The largest totals on the map are shown in the northeastern suburb of Ankeny with one report topping five inches. Totals quickly dropped off to the immediate north and south of Des Moines with some isolated 2+ inch amounts in other locations in the state.

Tuesday was a spectacular day in Iowa with warm temps and comfortable humidity levels. The featured chart presents the average dew point at a given observed air temperature for June. That average value is then used to compute the relative humidity at that temperature. Please note that the average dew point is computed by averaging the observed mixing ratios rather than a simple average of the observed dew points. In general, the relative humidity falls as the temperature warms, which makes sense as the heating of the air during the day time happens faster than water can be evaporated into it. You can generate this chart on the website for other reporting locations and other months / seasons of your choice.

The remnants of Tropical Storm Bill are currently bringing significant rainfall over the southern plains. The featured map displays five day forecasted precipitation totals from the Weather Prediction Center. The swath of heavy rainfall from this storm system is forecasted to stay to Iowa's south with Iowa's rainfall thanks to storm systems arriving from our west.

Earlier this week, the average dew point at a given temperature was featured. Today's feature show the combination of average dew point for a given wind direction. On Thursday, dew points were comfortable with a northerly wind. The featured chart shows a clear relationship between the wind direction and the average dew point for June at Des Moines. Of course, our major source of humidity comes from the south, so it would make sense that our dew points are higher with a southerly wind.

The NWS issued a Tornado Watch for much of southeastern Iowa on Saturday afternoon. Polk County (Des Moines) was initially included in the watch, but was removed after just 1 hour and 49 minutes as the storms fired east of the county. The featured chart looks at the frequency of tornado watch duration for the county. Two lines are plotted, the initial line represents the watch duration as initially issued, the final line presents what the final result for duration was (some watches/warnings can be extended in time / cancelled early). So having a 2 hour tornado watch is about a 1 in 10 frequency based on data back to 2005.

Two rounds of severe weather made for a rough day in Iowa on Monday. The featured map displays NWS Local Storm Reports. The morning saw a storm complex bring heavy rain and very strong winds to northern Iowa. Around noon, storms dumped large hail over east-central Iowa. The evening saw strong storms develop over southeastern Iowa with tornadoes and hail reported.

High temperatures on Tuesday were close to average for much of the state, which is typical for this time of year as shown by the featured chart. The chart displays the percentage of years that the high or low temperature is within five degrees of the NCDC climatology for the location, in this case Ames. The summer months are generally above the 50% value, which means that for a majority of the time the high or low temperature is within five degrees of average. This is thanks to warm ground temperatures and elevated humidity levels that help dampen most wild swings in temperature.

Numerous rounds of heavy rainfall producing thunderstorms have left some gaudy totals over central Iowa. The featured map displays estimated 48 hour rainfall totals from the NOAA MRMS project. A few reports have already trickled in this morning of between six and seven inches within just the past 24 hours. Flooding and Flash Flooding is definitely a concern as these heavy rainfall patterns are oriented in a NW to SE line, which matches the orientation of most river basins in the state.

The featured table presents top NWS COOP rainfall reports from Thursday along with the record maximum for the nearest long term climate site and the last 3+ inch rainfall for that site. The Perry report of 5.62 stands as the largest total for the site on record as indicated by the unofficial IEM archives. It is interesting to see that for two of the sites, the most recent 3+ inch rainfall was less than a week ago! While more rain is in the forecast, hopefully we can avoid these high of totals.

The seemingly constant stream of daily scattered showers and thunderstorms has made for a very wet June after perhaps the wettest month on record for the US in May. The featured map looks at the longest period since 1 May that the location went without receiving at least 0.05 inches of rain over a given hour. The chart nicely shows the areas that have had difficulty with spring field work as these long stretches are necessary to make fields passable by heavy equipment. The forecast for this week continues the recent pattern of daily chances of rain.

The smoke from Canadian wild fires was very noticeable in Iowa on Monday and made for a red colored sun. The featured map is visible satellite imagery with the smoke plume highlighted coming south out of Canada and into Iowa. Our upper air flow pattern looks to maintain this transport, so we may be seeing more of the smoke.