July 2019: Prolonged stretch of abnormally wet weather comes to an end, along with notable hot and humid conditions.

July 2019 signaled the end of a persistent and historic stretch of abnormally wet conditions across Illinois, along with several notable periods of significantly above average temperatures.

Preliminary data suggest that July 2019 concluded drier than average, with temperatures above the long-term average. The preliminary average statewide July temperature was 77.3°F, which is 1.9°F above the long-term average. The preliminary average statewide precipitation was 3.23 inches, which is 0.85 inches below the long-term average.

Data are provisional and may change slightly over time


After seven consecutive months of above average statewide precipitation, July 2019 marked the end of the historic wet streak with below average statewide precipitation for the first time since November 2018. Despite the overall below average designation, July precipitation across Illinois was not evenly distributed.

Many in southern and northeastern portions of the state experienced near to above average precipitation totals in July, with a station near Highland (Madison County) reporting the highest monthly rainfall total of 9.02 inches. In contrast, large regions of western and central Illinois saw below average rainfall. In fact, multiple localities near the Quad Cities and along the Mississippi River, as well as smaller regions in east-central Illinois received only 10 to 25% of average monthly precipitation (see maps below).

Dating back to June 1, these same regions have reported precipitation departures of around 2 to 4+ inches below the long-term average. This extended stretch of dry conditions prompted the August 1 map from the U.S Drought Monitor (using data through July 30) to continue to highlight areas of abnormally dry conditions across the western and central portions of the state.

Illinois Precipitation Departures Map
Midwest Regional Climate Center (MRCC), accessed 8/1/2019
Illinois Drought Map
U.S Drought Monitor (UDSM) Illinois, accessed 8/1/2019

Interactive July 2019 Climate Station Precipitation Map


Despite an overall seasonable and pleasant ending, the first weeks of July brought several extended periods of heat and humidity to Illinois. Most notable was the heat wave that impacted the region from July 18 through July 21, in which every county in Illinois was under an Excessive Heat Warning at some point during the weekend. Throughout this event, daily maximum station temperatures soared into the 90s, with dew points in the mid- to upper 70s. This resulted in heat indices over 100 for many and approached 110 or higher in some localities. Daily temperature departures of 8 to 10+ degrees above average were common across the northern half of the state (see map below).

Illinois July Heatwave Map

Overnight low temperatures during this event did not bring much, if any, relief from the heat. With a daily minimum temperature of only 80 degrees on July 19, Rockford (Winnebago County) set a new all-time record-high minimum temperature. Records for Rockford extend back to 1905.

Looking at July as a whole, the average station temperatures varied from the mid-70s to the low 80s, and monthly temperature departures of 1 to 4 degrees above the long-term average were common for the northern two-thirds of Illinois (see maps below). The highest temperature reading in the state of 98 degrees occurred at two stations, Flora (Clay County) on July 11, and Palestine (Crawford County) on July 21. The lowest minimum temperature of 51 degrees also occurred at two stations, one near Champaign (Champaign County) on July 23, and at a station near Paxton (Ford County) on July 25.

Illinois July Average Temperatures

Ilinois July Temperatuer Departures

Interactive July 2019 Climate Station Temperature Map

August 2019 Outlook

For the remainder of August, the monthly outlook from the Climate Prediction Center (CPC) issued on July 31 favors probabilities for below average temperatures across Illinois and most of the upper Midwest. The outlook also favors near equal chances for below, near, or above average precipitation.

CPC August 2019 Temperature Outlook
August 2019 Temperature Outlook
CPC August 2019 Precipitation Outlook
August 2019 Precipitation Outlook

Dryness Continues in Central Corn Belt

Summary: Rapid drying has occurred across the central Corn Belt since June 1 as virtually no rain has fallen, including most of central and northern Illinois. In addition, high water demand on soils has caused soil moisture to steadily drop in sites across Illinois. Estimates at one location in central Illinois put the water loss from evaporation in the soils and transpiration from plants at 2.4 inches since June 1.
When we get this short-term combination of little rain, high temperatures, and high evapotranspiration rates in summer months, we call it a “flash drought” because conditions can deteriorate rapidly such as they did in the 2012 drought. In my opinion, we are not quite there yet, but we could be if this continues for another few weeks.

Current Conditions and Forecast

Rainfall: Here is the map showing the dryness across the central Corn Belt since June 1. The area shaded gray has had almost no rain at all. Areas in orange have received 0.1 inches or less.
Continue reading “Dryness Continues in Central Corn Belt”

Drought Monitor Says Abnormally Dry – Should We be Worried?

The US Drought Monitor introduced their D0 “abnormally dry” category across northern and western Illinois (first map). Should we be worried? We have been running about 2 to 4 inches below average on precipitation this winter (second map) – that’s both rainfall and the water content of any snow. The good news is that the demand for water is very low in winter. Therefore, the impacts on soil moisture, stream flows, and lake levels so far have been minimal.

Click to enlarge. http://droughtmonitor.unl.edu/

Continue reading “Drought Monitor Says Abnormally Dry – Should We be Worried?”

Thursday Highlights – Drought Monitor and El Nino Forecast

Here are two highlights for today:

U.S. Drought Monitor

After some concerns of dryness over the last several months in parts of Illinois, the conditions across Illinois were much wetter in the last two weeks. Rainfall totals were especially heavy south of Interstate 72 and ranged from 3 to 8 inches or more (see map below).

The U.S. Drought Monitor has removed all areas of drought in Illinois and greatly reduced the region of “abnormally dry” conditions.


Climate Prediction Center El Niño Forecast

The NOAA Climate Prediction Center issued a new El Niño Watch today, saying …

While ENSO-neutral is favored for Northern Hemisphere spring, the chances of El Niño increase during the remainder of the year, exceeding 50% by summer.

This reflects a slightly stronger chance of El Niño arriving this summer than mentioned in their post a month ago. However, they caution that there is still a great deal of uncertainty in the timing and strength of the El Niño and recognize that the skill in forecasting El Niño this early in spring is low. This is a less certain forecast than the one issued by the Australian Bureau of Meteorology earlier this week, indicating that there was a greater than 70 percent of an El Niño event by June.

Nation Cut in Two by Drought

Click to enlarge.
Click to enlarge.

The latest US Drought Monitor map from May 14, 2013, shows a Dr. Jekyll/Mr. Hyde nation when it comes to drought. Much of the country to the west of the 96° longitude is in some stage of drought while the country to the east of that line is largely drought free for the moment. Hardest hit have been the Plains states which in some cases are in year 2 or 3 of this drought.
By the way, the US Drought Monitor began about 13 years ago to provide one, unified map of drought across the United States. It is produced in partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration with lots of input from scientists, state climatologists, state and local agencies, university extension, landowners, farmers, etc.  Maps are updated weekly and released on Thursday mornings.
Click to enlarge.
Click to enlarge.

The precipitation pattern so far this year reflects these differences between east and west. The map is the current year to date departure from average precipitation produced by the NWS. Areas in green and blue are 2 to 8 inches above average and include much of the Midwest and Southeast. Areas in yellow are 2 to 6 inches below average. Hardest hit so far has been the West Coast with departures more than a foot below average.  There are large areas shaded gray which show near-average conditions. However, much of the west needs many more months of average precipitation or even above-average precipitation to start a recovery from their current drought situation.
Click to enlarge.
Click to enlarge.

The National Climatic Data Center has a product that gives a rough idea of the amount of precipitation needed over the next 6 months to recover from drought. I say “a rough idea” because the timing and intensity of the precipitation is important as well. The effect of getting 3 inches in 30 minutes is different than getting 3 inches over 3 days. The first will cause lots of runoff while the second will have a better chance of recharging soil moisture. As you can see, it will take a considerable amount of precipitation in the Plains states to get out of their current situation.

Good News on Soil Moisture

The Illinois Weather and Crops report was released today by the USDA. As of March 24, the statewide topsoil moisture looked great with 81 percent “adequate” and 11 percent “surplus”. There was some lingering dryness across central Illinois. However, that was before Sunday’s storm that dropped a lot of snow whose water content ranged from 0.5 to 1.5 inches in that region.
Subsoil soil moisture was a little more pessimistic. Statewide numbers included 11 percent “very short”, 26 percent “short”, 58 percent “adequate”, and only 5 percent “surplus”. Some of the lowest numbers were in the northern and western part of the state. Subsoil moisture is not critical in the spring but provides a useful reserve, or cushion, during periods of dry weather in the summer.
The Illinois Weather and Crops is coming off it’s typical winter schedule of once per month to it’s growing season schedule of once a week. The reports can be found here. You can get the reports automatically by subscribing here.

Table from the USDA report, click to enlarge. 


Guidelines on soil moisture (USDA)

Topsoil is defined as the top six inches. Subsoil is defined as the area from six inches below the surface to a depth of three to four feet.
Very Short – Soil moisture supplies are significantly less than what is required for normal plant development. Growth has been stopped or nearly so and plants are showing visible signs of moisture stress. Under these conditions, plants will quickly suffer irreparable damage.
Short – Soil dry. Seed germination and/or normal crop growth and development would be curtailed.
Adequate – Soil moist. Seed germination and/or crop growth and development would be normal or unhindered.
Surplus – Soil wet. Fields may be muddy and will generally be unable to absorb additional moisture. Young developing crops may be yellowing from excess moisture.

Illinois Drought Free

According to the US Drought Monitor, Illinois is now drought free for the first time since April 3, 2012. Most areas in Illinois have seen positive responses in soil moisture, stream flows, lake levels, and groundwater levels since the fall. A small area of northwest Illinois remains as abnormally dry due to some lingering concerns about subsoil moisture and groundwater levels in that area.

USDA Report Reflects Impact of Drought in Illinois

Last week the Illinois office of the National Agriculture Statistics Service released their report on crop yields in Illinois. The full report can be found here.
As expected, the Illinois corn yield for 2012 was only 105 bushels per acre, 52 bushels below last year. They noted that this was the lowest yield since 1988, when the average yield was only 73 bushels per acres. Because of the severe conditions of the corn crop, almost twice as many acres were harvested for silage in 2012 than in 2011.
Illinois soybean yield for 2012 was 43.0 bushels per acre, down 4.5 bushels from 2011. This was the lowest soybean yield since 2003, when the average yield was only 37.0 bushels per acre. While too late to do much good for corn, rains in the second half of August and the remains of Hurricane Isaac over Labor Day weekend may have provided some benefit to soybeans.
The one bright spot in the Illinois report was winter wheat production. The yield in 2012 was 63 bushels per acre, up 2 bushels from 2011. However, only 660,000 acres were seeded in the fall of 2011, which is down 140,000 acres from the previous fall. I suspect the decline was due in part to the already dry conditions experience in southern Illinois – the primary production area of the state.

January in Illinois – Wet Despite the Lack of Snow

The preliminary numbers are in and the statewide precipitation was 3.9 inches, 1.9 inches above average. Most of the state was in the 3 to 6 inch range except for some drier areas in central and western Illinois. It was wettest in southeastern Illinois with several sites with over 6 inches, including Smithland Lock and Dam on the Ohio River with 9.7 inches. By the way, the precipitation amount includes both rain events and the water equivalent of any snow.
Snowfall for January was below average and ranged from 6.5 inches in the northwest corner to zero in far southern Illinois (second map).
Even though January finished with below-average snowfall, it was offset with above-average rainfall in many areas. The impact of these rains were discussed in an earlier post.  As a result, the U.S. Drought Monitor has reduced the area in drought or abnormally dry conditions since January 1 (last figure) by 11 percent.
The statewide temperature for January was 28.7 degrees, four degrees above average. It was far short of the warmest January on record that was established in 2006 with 37.9 degrees and followed closely by 1933 with 37.7 degrees.

January precipitation (rain plus water content from snowfall).
January precipitation (rain plus water content from snowfall).

January Snowfall for Illinois.
January Snowfall for Illinois.

Change in the US Drought Monitor for Illinois through January 2013.
Change in the US Drought Monitor for Illinois through January 2013.

Widespread Rain Across Illinois

I was driving back from a meeting yesterday and saw creeks that were bank full and water standing in fields. That’s the first time I’ve seen those sights in a while, maybe over a year ago in this part of Illinois (Champaign County).
In the last 7 days, widespread rainfall amounts of 1 to 3 inches have been reported across the state. See the map below. This is a National Weather Service product that combines high-resolution radar estimates calibrated with rain gauge measurements (see map below). The heaviest rains fell in northern Illinois, an area considered to have been in some stage of drought earlier this week. Because some of the rain fell after the cutoff for this week’s Drought Monitor, I would expect to see the effects of these rains in next week’s map.
Another bit of good news is that the soils appeared to be unfrozen across most of the state during this rain event, thanks to the warm temperatures early in the week. See the second map below from our network of 19 soil temperature sites across Illinois. As a result, much of this rain should have had a chance to soak in and recharge the soil moisture profile.
Finally, the abundant and widespread rainfall across the state has increased the flow in streams and rivers across the state. Many stream gauges report levels that are in the upper 90th percentile for this time of year. In fact, the National Weather Service has reported some minor flooding along the Kaskaskia and Little Wabash Rivers. The result is that much more water is flowing into the critically low Mississippi River. The Mississippi River stage at Chester Illinois (below St. Louis) has risen seven feet and is expected to rise another four feet in the next day or two (last figure).
While the recent rains should provide some temporary relief for barge traffic on the Mississippi River, levels are expected to start dropping again in a few days. The larger problem is that about 80 percent of the Missouri River and Upper Mississippi River basins are in some stage of drought, according to the U.S. Drought Monitor. Until those two basins are in better shape, concerns with Mississippi River flows will remain for some time.

Seven-day precipitation totals ending January 31, 2013.
Seven-day precipitation totals ending January 31, 2013.

Soil temperatures at the 4 inch level under grass at 19 sites around Illinois for January 30, 2013. Data are from the Water and Atmospheric Monitoring (WARM) network at the Illinois State Water Survey.
Soil temperatures at the 4 inch level under grass at 19 sites around Illinois for January 30, 2013. Data are from the Water and Atmospheric Monitoring (WARM) network at the Illinois State Water Survey.

Observed Mississippi River levels at Chester Illinois on January 31, 2013, and forecasted river levels into February.
Observed Mississippi River levels at Chester Illinois on January 31, 2013, and forecasted river levels into February.