Clear skies overhead this weekend give satellites a great look at the ground to show what has happened to our landscape over the past month. The featured image is of Aqua MODIS true color imagery from 6 September and 1 October of this year. Our lush green landscape has been replaced by the brown shades of fall. This color change is important as it changes the albedo of the surface allowing warming to occur more rapidly. This change will be in effect this week with mostly clear skies expected to push temperatures to near 80.

Temperatures soared to 80 degrees in some locations in Iowa on Monday and even warmer temperatures are expected today. The featured chart looks at the longest streak of daily high temperatures over 80 by month. The year on which the last streak of the given length occurred is presented as well. It does not appear we'll break the 80s streak in October this year, but temperatures will not be far from 80 for the entire week!

Tuesday was yet another spectacular day in Iowa with a warm breeze pushing high temperatures into the 80s for some. It also made the third day in a row that high temperatures were 40+ degrees warmer than the morning low temperature. The featured chart looks at the longest streak of having daily warmups over 40 degrees by month for Ames. Getting a streak of these days looks rare in deed, the October record of 4 looks hard to break today as low temperatures this morning are around 50 instead of in the 30s.

Our recent stretch of warm weather has also been accompanied by very dry conditions making for a dangerous fire setup. The featured chart presents relative humidity from the Ames Airport sensor since the first of June. The end of the growing season is also the end of a water source in the atmosphere from plants. Our vegetation helps keep humidity levels higher during the summer time as can be seen by the minimums in the plot during the summer above 40%.

The last year in Iowa has been dry for most, but is the first dry year in the last 5 or so. The featured chart looks at the accumulated precipitation departure from today back the given number of days for Ames. Over the last 365 days, the departure is around 5 inches below average. If one looks at longer periods, the deficit quickly becomes a surplus over the past 3 years with departures around 20 inches on the wet side of average! There is a bit of rain in the forecast, but the heaviest totals will fall to our southwest where they need it the most.

Some rain showers are finally working into the state this Monday morning after a remarkable stretch of warm and dry weather. The featured map presents an estimate of the number of days since the last daily quarter inch daily rainfall. Western Iowa missed out on the most recent storm system in September that brought a number of days of rain to Eastern Iowa. The rain chances look to persist through mid week.

The remarkable stretch of warm October weather is about to experience a slight cool off, but still be above average. The featured chart presents the average high temperature for the first 10 days of the month and many sites averaged 80 or better! Considering that daily climatology is now in the lower 60s, this was quite warm.

The featured chart presents the average high temperature for Ames for the first 11 days of October. This year has been the warmest since 1997. In the past decade, only 2009 was below average and it was one of the coldest on record. The forecast has our daily high temperatures creeping closer to climatology in the 60s as it will truly start feeling like fall!

The water year covers a period from 1 October until 30 September of the next year. The thought is that precipitation after the first of October goes toward next year's plant use and snowfall equates into runoff during the next spring. The featured chart presents the water year precipitation totals along with the year over year change in this total. This year's total represents the third largest drop in precipitation. Of course, the largest was 1994 after the epic rains of 1993.

Our past 12 days have seen daily high temperatures above climatology making for the longest streak this year. The featured chart presents the daily streaks above or below (negative numbers) for Ames since the beginning of last year. Last year also saw a long streak in October with highs above average. Our streak this year will end soon with reality setting back in. The bottom plot shows the streaks for low temperature and our warm nights in July certainly stick out.

Our temperatures have recently returned to near average for this time of year after a very warm start to the month. The featured chart looks at the past 11 years for each day in October whether it was above or below the 30 year climatological average. This October 17th will not make it above average with the rest of the week set to follow in that pattern. High temperatures on Wednesday look to only be in the 40s!

The minimum temperature so far this fall has been on the warm side of average with many locations yet to experience a sub freezing temperature. The featured plot presents the percentile value for the fall minimum temperature against all previous recorded fall seasons for the given location. Cold temperatures are in the forecast and most will experience sub freezing temperatures this week.

The featured chart presents an IEM estimate of the areal coverage of Iowa that has experienced its first fall season sub-freezing temperature. The blue line is the simple average of the previous 60 years with the red and green line being the previous two years. The first two weeks of October are typical for having the first frost of the year with the warmer parts of the state lasting longer into October. It appears likely that the rest of the state yet to experience a freeze will see it in the coming days with very cold air settling into the state.

With our recent few days of temperatures well below average, one wonders how many warm days are left this year! The featured plot presents the observed frequency of having a given number of days with a high temperature at or above a given temperature from now until the end of this year. For example, 80% of the years since 1893 experienced a high temperature of 70 on at least one day, but only 20% of the years experienced a total of 7 days at 70. The forecast puts us back into 60s after a chilly day today in the lower 50s.

Yesterday the chances of seeing warm high temperatures yet this year were featured, so naturally it is time to do the opposite and see how cold it will get in the next two and a half months. About 80% of the years since 1893 have seen at least one day with a low temperature around zero and about 7 days at 10 degrees. Thankfully, the near term forecast does not have temperatures approaching anything on the chart.

The featured map presents IEM estimated precipitation departures since the beginning of September. The central sections of the map have missed out on the rain with totals below 40% of average. The near term forecast looks to continue the dry weather with temperatures near climatology.

The featured chart presents the monthly precipitation departures from average for Des Moines since January 2005. We are currently working on a streak of four consecutive months below average, which would be the longest streak since the end of 2005. This October is not done yet, but the forecast has no hint that we will make up the difference before November rolls around.

Our weather has made a dramatic change after a very warm Tuesday followed by a cold front which has dropped our temperatures 10-20 degrees versus yesterday morning. The featured map presents an analysis of this change showing the area of cooling near Iowa paired with an area of warming over the mid Mississippi valley. This couplet is due to air mass translation as the area of warm air moves east and is replaced by a cold air mass. Our high temperatures look to be stuck in the 50s until a slight warm up next week.

The high temperature on Wednesday was more than 20 degrees colder than the high on Tueday making for the largest one day drop in temperature for Ames since early June. The featured chart presents the day to day changes in high temperature for this year along with the daily maximum and minimum value since 1893. Day to day variability is much less in the summer time thanks to the moderating effects of water vapor in the air, warm ground temperatures, and more direct solar angle.

So far, Des Moines has had its 12th driest meteorological fall on record. The featured chart presents the precipitation rank to date since the first of September for this year, 1914 (the wettest year) and 1966 (the driest year). If we got no precipitation for the rest of the season, our fall total would still be a bit higher than 1966 and coming in second lowest. The forecast has some chances of rain in the forecast next week.

Days with rain have been hard to come by the past two months. The featured chart presents the observed daily frequency of measurable rain for the period prior to 1971 and for the period after. October is shown has one of the months with an increased frequency of rainfall, but this year has gone against that trend. Rain is in the forecast to start off November.