July in Illinois – Cool and Dry

The preliminary numbers are in and this July in Illinois was cool and dry. The statewide average temperature was 73.3 degrees, 2.0 degrees below the 1981-2010 average. It currently ranks as the 19th coolest July on record. Statewide records go back to 1895.

The statewide average precipitation was 2.74 inches, 1.31 inches below the 1981-2010 average. It currently ranks as the 29th driest July on record.

Despite the dry July, the statewide total precipitation for 2013 stands at 31.48 inches at end of July and 7.61 inches above the 1981-2010 average. It is the second wettest January-July. The wettest January-July was set just a few years ago; 2008 with 32.52 inches.

The rainfall in July was unevenly distributed across state. Much of central and northern Illinois were 1 to 3 inches below average while southern Illinois was several inches above average. See maps of accumulated precipitation and departures from average.

Mt. Vernon reported the highest monthly total in the state with 9.42 inches, followed closely by Olney with 9.15 inches. On the dry side, Joliet reported one of the lowest monthly totals with 0.63 inches along with 0.72 inches in Pontiac and 0.77 inches in Kankakee.

The wet spring and cool July have both helped to reduce the impacts of the dry weather so far but conditions will be watched closely in August.

Note: we had some technical difficulties so the maps are through July 30 instead of July 31. There was not much rain on the radar on July 31 so the maps are still fairly representative.



July 2012 and 2013

What a difference in temperature between July 2012 and 2013. Last year we were in the midst of a full-blown drought and heat wave with temperatures routinely in the 90s and low 100s. The statewide average temperature for July 2012 was 81.8°F (6.5°F above the 1981-2010 average) and the second warmest July in Illinois behind the record of 83.1°F in 1936.

This July has had its hot and humid moments, but for the most part has been mild overall in Illinois. The statewide average temperature for July 2013, as of July 29, is 73.6°F ( 1.7°F below the 1981-2010 average) and the 23rd coolest July on record based on preliminary data.

The cool July weather was confined to the central and southeastern US. Meanwhile, both the western and northeastern US have experienced warmer than average temperatures this month.

Figures. July 2013 compared to July 2012 in terms of temperature departures from average.

Temperature Departures for this July through the 29th. Cool weather prevails across much of the lower Midwest.
Temperature Departures for this July through the 29th. Cool weather prevails across much of the lower Midwest.
July 2012 - toasty indeed.
July 2012 – toasty indeed.

Abnormally Dry Weather Creeps into Western Illinois

The latest US Drought Monitor has an area of “abnormally dry” conditions in western Illinois. This does not mean drought but it means that it is an “area of interest” to paraphrase what they say on TV when they have suspicions about someone but have no hard evidence.

In this particular case, the only evidence are widespread watering in towns and stressed corn and soybeans – especially the late planted fields with shallow root systems.

Rainfall amounts in those areas have been small and widely scattered (second figure). For example, Quincy airport has received only 0.25 since July 1. Combined with the high rates of evapotranspiration in July, roughly two-tenths of an inch per day, this situation can lead to the rapid withdrawal of topsoil moisture. Other areas in north-central Illinois may be candidates for the “abnormally dry” status in coming weeks if the rains do not return.



July 2013 versus July 2012

I received the latest crop development report yesterday and was amazed by the contract from a year ago. The July 23, 2012, report noted that top soil moisture was 99 percent short to very short and 80% of that was in the very short category. Fast forward to the July 22, 2013, report and topsoil moisture was 27 percent short to very short only 2 percent of that was in the very short category.

Statewide Topsoil Moisture (USDA-Illinois)
Very Short Short Adequate Surplus
July 23, 2012 80 19 1
July 22, 2013 2 25 64 9

The US Drought Monitor looked a lot different between this year and last year in July (see figure below). Last year on July 24, 2012, all of Illinois was in some stage of drought and 71 percent was in the two worst stages. This year at about the same time – drought free.

We are watching conditions in western Illinois for developing dryness if they continue to miss the rains.


Latest Outlooks from NOAA

NOAA Outlooks

Well, I guess no news is good news. While the latest monthly and seasonal outlook from NOAA (first figure) yesterday called for hotter conditions in the West and wetter conditions in the Southeast, we are stuck in the middle with EC – equal chances of above, below, and near-normal temperature and precipitation.


U.S. Drought Monitor

The July 16, 2013, US Drought Monitor map for the Midwest – drought free in Illinois, Wisconsin, Michigan, Indiana, Ohio, and Kentucky. There are a few spots of “abnormally dry” in Missouri, Iowa, and Minnesota.


Heat-Related Deaths in the US

Considering that parts of the United State are in the grips of a heat wave, I created a graph (below) of U.S. heat-related deaths from 1986 to 2012. The outstanding years were 1995 primarily due to the over 700 deaths associated with the Chicago heat wave and the 1999 where another 100 deaths were associated with Chicago. In general, the graph shows that heat wave deaths have been higher since the mid 1990s than before. However, that pattern may be due to poor reporting of heat deaths before 1995.

Another interesting feature was that despite the high heat and prolonged drought last year (2012), the number of heat-related deaths was about the same as the two years before (2010 and 2011). One likely reason for that – at least for Illinois and the Midwest – was that while the air temperatures were high in 2012, humidity levels were lower due to the ongoing drought.

I am not an expert on heat wave deaths. However, I do know that deaths related to heat waves are hard to track down. Even coming up with the number for the 1995 Chicago heat wave was a challenge. In addition, heat may be a contributing factor in the death of someone already ill but not the real cause of death. So the true impact of heat is likely under-reported.

Results of the 1995 Chicago heat wave have shown that the elderly and low-income groups are most vulnerable. Also heat waves early in the summer are more deadly because people have not become acclimated to hot weather yet. Another important factor in heat-related deaths are the night-time temperatures. It’s hard to rest and recover from the day’s heat if it continues to stay exceptionally warm at night. Finally, many of the fatalities are not on the first day but increased in occurrence as the heat wave persists.

Figure 1.
Figure 1.

First Half of July – Dry Across Much of Illinois

We have seen little precipitation over much of Illinois in the first half of July. The map below shows that much of the state has received less than an inch of precipitation. The only area with significant precipitation is along and south of Interstate 70 with amounts of 2 to 5 inches.

It is not a major concern yet given the wet conditions in May and June. In fact, if you look at the precipitation departures for the last 90 days ending on July 16 (second map), you see that much of the state remains 1 to 12 inches above the 1981-2010 average.

According to the National Weather Service, the next chance for significant precipitation is this weekend as a cold front pushes through the state. This should trigger rain ahead of it and give some relief from the heat and humidity of this week.

July 2013 precipitation through July 16.
July 2013 precipitation through July 16.
Precipitation departures from the 1981-2010 average for the last 90 days in Illinois.
Precipitation departures from the 1981-2010 average for the last 90 days in Illinois.