[Updated July 20 for a more frequently updated map from the Climate Prediction Center]
People have asked me several times this week, “how much rain do we need to end the drought?”
There is no easy way to answer this. The normal rainfall per week in Illinois is about an inch. So we need that inch per week just to keep from slipping farther behind. Taking it a step farther, that means you need well over an inch per week to start recovering from drought. Of course, no amount of rain at this point will undo the damage done to crops already.
There is one product, based on the Palmer Hydrological Drought Index, that attempts to answer this question from the Climate Prediction Center. However, I would treat it as an estimate. Even so, it gives you an idea of how far we have to go for a recovery. They estimate that we would have needed 9 to 15 inches of rain across much of Illinois to end the drought. That is a tall order. The wettest July on record for Illinois is 8.03 inches in 1958 and the wettest August on record was 6.91 inches in 1977.
Personally, I’m not sure it would take record-breaking rainfall. And I’m not sure we want 9 to 15 inches over the course of one or two months because that could lead to all kinds of other problems like flooding and heavy soil erosion.
Based on past droughts in Illinois, a month with rainfall 50 percent above normal (around 6 inches) followed by several months with near-normal rainfall would be capable of turning things around without the more serious consequences of heavy rainfall.
The U.S. Drought Monitor just increased the drought coverage in Illinois to 100 percent. In addition, the area of D2 “severe drought” expanded in eastern Illinois and east of St. Louis and along the Illinois-Wisconsin border.
The statistics for July so far (July 1 – 11) show why the drought has worsened so quickly. The statewide average precipitation was 0.5 inches, just 37 percent of what we would normally receive in the first 11 days of July. The statewide average temperature during this time was 83.1 degrees, 7.5 degrees above normal.
The table that accompanies the map has some interesting statistics. A year ago at this time there was no drought in Illinois thanks to an exceptionally wet spring and early summer. And this year started out with no drought in Illinois. Even three months ago only a small part of southern Illinois (5 percent) was considered in a moderate drought.
The U.S. Drought Monitor is a joint effort between NOAA, USDA, and the National Drought Mitigation Center. They do consider local input on drought impacts. If you have any impacts – text and/or picture – that you would like to include for consideration, please contact me at firstname.lastname@example.org – thank you.
Here are some photos from our student intern that shows conditions on a farm near Sigel Illinois. They were all taken on or around July 1.
Here are some photos I took in Champaign County this afternoon (July 5), just west of Champaign. At the time it was 99 degrees, according to Willard Airport (Champaign).
If you have any pictures of the impact of this year’s drought that you would like to share, please let me know. I’m especially interested in pictures related to agriculture or water supplies (ponds, rivers, lakes). Just send me a note in the comments and I’ll get back to you to work out the logistics. Thanks.
Here are the statewide Illinois monthly temperature and precipitation departures from the 1981-2010 average for both 2011 and 2012. We have had a run of above-average temperatures since October 2011 and a run of below-average precipitation since January of 2012. The latest outlooks published on June 30 by the National Weather Service shows that the odds of this pattern of warmer and drier conditions to prevail through July (bottom figure).
The current drought condition has many similarities with 1988. Here is the departure from normal precipitation for the Midwest from April 1 to July 2 for 2012 (left) and for 1988 (right).
Areas in green are doing well. Areas in blue are having to deal with flooding issues. Areas in yellow are dry, and areas in the darker shades of yellow, orange, and red are progressively drier.
This year the drought has missed parts of Minnesota, Wisconsin, and Michigan, where all the Midwestern states suffered in 1988. So far this year, the hardest hit area is in southern Illinois, southwest Indiana, western Kentucky and southeastern Missouri with departures of 8 to 12 inches (dark orange and red areas) since April 1. In 1988, those same conditions were seen over a wider area including large parts of northern Missouri, Iowa, Illinois, Indiana, western Kentucky, and eastern Ohio.
The latest USDA Illinois Weather and Crops report was released this afternoon. The topsoil conditions were rated at 52 percent “very short” and 37 percent “short” and only 11 percent adequate. Soil moisture conditions were best in northern Illinois, and deteriorated southward. Hardest hit was southeastern Illinois with 100 percent of the topsoil and 100 percent of subsoil rated as “very short”.
The corn crop was rated at 12 percent “very poor” and 21 percent “poor”. The soybean crop was rated at 11 percent “very poor” and 20 percent “poor”.
Several people have compared this year to 1988. How bad was soil moisture in 1988? According to the USDA report for July 5, 1988, the entire state was listed as 100 percent “very short” on topsoil moisture. However, they rated the corn crop at 2 percent “very poor” and 20 percent “poor”. The soybean crop was rated as 2 percent “very poor” and 14 percent “poor”. So they rated the soil moisture to be in worse shape yet they rated the crop to be in better shape in 1988, compared to 2012. It’s hard to make sense of the numbers. Of course, these are subjective ratings and the procedure for rating crops and soils has likely changed with time.
The hot and dry weather continued in Illinois for June. The statewide average temperature for the month was 72.9 degrees, a full degree above normal. There were a few cool periods during the month, but everyone will remember the hot ending to the month with highs in the upper 90s and low 100s. Some 56 sites broke daily records on June 28 and 29. While the month was warm, it is far behind the hottest June on record* in Illinois, 1934 with a state-wide average temperature of 78.5 degrees.
Every month this year has had above-normal temperatures. As a result, the statewide average of 52.8 degrees for the last 6 months is the warmest on record. It beats out a similar period for 1921 when the statewide average temperature was 52.1 degrees.
The statewide average precipitation for June was 1.77 inches, which is 2.3 inches below normal and 43 percent of normal. It was the eighth driest June on record. June 1988 was the driest on record at 1.05 inches.
The statewide average precipitation for the first half of 2012 was 12.58 inches, making it the sixth driest on record. The first half of 1988 was slightly worse at 12.00 inches. The driest January-June was 1934 with only 10.33 inches.
*statewide records go back to 1895.
Here is the June precipitation expressed as a total accumulation, a departure from normal, and percent of normal.