As of April 25, the statewide average precipitation for Illinois is 2.8 inches, which is 94% of normal. However, we have several opportunities for widespread rains this week and into the weekend, according to the NWS precipitation forecast.
The first round of rain on Wednesday and Thursday has potential rainfall amounts of 1 to 2 inches across most of Illinois, along with the chance for severe weather. Continue reading
Highlights: The 12th wettest August in Illinois finishes out the 10th wettest summer on record. While August was slightly warmer than average, the summer was cooler than average. Here are the statistics.
The statewide average precipitation for August was 5.18 inches, 1.59 inches above average and the 12th wettest on record. The wettest area of the state was Cook County. The largest monthly total was from a CoCoRaHS site (IL-CK-100) in Cicero with 10.20 inches of precipitation.
This first map shows several areas across the state with amounts of 7 to 10 inches (oranges and reds), according to radar estimates. There were a few areas in the northwest and east-central Illinois with only 2 to 3 inches. The second map shows the departures from average, showing the many areas with 2 to 8 inches above average for the month.
After a wet start to the 2014 growing season, we have seen a significant drop in rainfall across parts of northern and central Illinois in the last few weeks. Here is the 30-day rainfall as a percent of average. Areas in the orange are 25 to 75 percent of average while the areas in red are less than 25 percent of average. There are reports of soil moisture running low in some areas. On the other hand, southern Illinois has received above-average rainfall in the last 30 days.
Besides the switch from too wet to too dry in northern and central Illinois, and too much rain in southern Illinois, the other issue is that temperatures have been running about 4 degrees below average for the past 30 days. We are getting some heat this week. However, the longer-term forecasts indicate a return to cooler temperatures and more rain after this week through September 1.
If you look at the last 90 days the heavier rains in June and early July masks the recent dryness (map below). In fact, at the 90 day time scale rainfall in Illinois is generally at or above long-term average (1981-2010), as denoted by the grays and greens. This is one of the challenges of drought monitoring – sorting out short-term dryness versus long-term wetness or vice versa.
The statewide average temperature for August so far is 72 degrees, 2 degrees below average. This follows on the heels of the cool July. The NWS forecast show that the mild temperatures will continue this upcoming week with highs in the upper 70s and low 80s in northern Illinois to the low to mid 80s in central and southern Illinois. The 6-10 and 8-14 day forecasts that extend out to August 21 point towards a continuation of cooler-than-average conditions.
All in all, it should be great weather for the Illinois State Fair. I can remember many years of the State Fair being hot and humid with your choice of either dust or mud. It’s a wonder the butter cow did not melt.
The map of observed precipitation below from the NWS shows that rainfall has been widespread and fairly heavy in western and southern Illinois with amounts ranging from 1 inch (green) to 5 inches (red). It is lighter and more variable in northern and eastern Illinois, ranging from 0.1 inches (light blue) to 2 inches (dark green). Much of that heavy rain to the east of St. Louis fell in a part of Illinois that was dry in July.
According to a press release from NASA …
Data from satellite sensors show that during the Northern Hemisphere’s growing season, the Midwest region of the United States boasts more photosynthetic activity than any other spot on Earth, according to NASA and university scientists.
They determined this by measuring the fluorescent glow that healthy plants give off when they grow. It is not visible to the human eye but can be picked up by special sensors on satellites. The press release has a lot more details.
If you click on the map, you can see the full version. While they don’t have any state boundaries, you can make out Lake Michigan. Based on that, it looks like one of the brightest areas is across central and northern Illinois – no surprise there.
The magnitude of fluorescence portrayed in this visualization prompted researchers to take a closer look at the productivity of the U.S. Corn Belt. The glow represents fluorescence measured from land plants in early July, over a period from 2007 to 2011.
Image Credit: NASA’s Goddard Space Flight Center.