I love all four seasons in Illinois but I especially like fall. In fact, you could say I’m a falloholic. What’s not to like – the air is cool and crisp and the cloud formations are spectacular. One of the best things about fall is the changing color in the trees, shrubs, and grass.
A great website for all things related to fall color is the University of Illinois Extension site called “The Miracle of Fall“. Check it out for fall color, foliage updates, photos, festivals, etc. You can also find out about fall activities in Illinois at the Office of Tourism site “EnjoyIllinois.com“. A few other sites to explore are:
One of things I get asked every year at this time is, “what is the effect of weather on this year’s fall color?” It’s hard to answer because there is no formula for this. In general, you don’t want drought conditions because the leaves just turn brown and fall off. Instead, you want nights to be cool but not freezing to trigger the change in leaves. Also, you want mild day time temperatures (not too hot) and sunny weather to really make the colors pop.
I hope you take time to enjoy fall in Illinois. I know I will.
The U.S. Drought Monitor has reduced the area in drought for Illinois (first map below). Generous rainfall in recent weeks (second map) along the northern and southern borders of the drought led to the reductions. It also helps that cooler temperatures and maturing field crops have reduced the demand on soil moisture.
Soil moisture measurements from a network of sites operated by the Illinois State Water Survey confirmed that soil moisture was recovering by September 28. The table below list the soil moisture at 2, 4, and 8 inches and are a percentage of the water by volume. For example, “24” at 2 inches in Belleville means that the water content of the soil at that point is 24 percent. For most soils in Illinois, values of 30 percent or more mean plenty of soil moisture, values in the 20 percent range are a little dry, and values in the 10 percent range are very dry. The very low values at Kilbourne are typical of the very sandy soil there. They tend to drain very quickly and are only high right after a significant rainfall events.
Location 2 in 4 in 8 in
Belleville 24 28 27
Big Bend 24 29 23
Bondville 17 17 33
Brownstown 24 22 23
Champaign 21 31 32
Carbondale 28 34 32
DeKalb 38 37 38
Dixon Springs 33 36 38
Fairfield 37 34 35
Freeport 36 37 42
Kilbourne 3 4 3
Monmouth 24 30 24
Olney 26 30 32
Peoria 32 35 35
Perry 17 15 18
Springfield 25 23 14
Stelle 32 34 29
St. Charles 33 38 39
Rend Lake 26 39 40
I think we will remember 2011 as a year of extreme events. In Illinois we have already faced a February blizzard, flooding, record rainfalls, drought, and a heat wave. The latest newsletter of the NOAA’s Regional Climate Centers Program has highlighted several major events from around the country, including:
The natural rhythm of soil moisture in Illinois is to be abundant in spring (sometimes to the point of water standing in fields), followed by a prolonged draw-down during the growing season. Historically, soils are usually at their driest at the end of August and early September. However, soil moisture begins to recover in the September/October time frame as the temperatures cool and crops are harvested, even if rains are below average.
We are seeing some recovery in soil moisture now, according to our soil moisture network maintained at the Illinois State Water Survey. Here is the average soil moisture in the top 20 inches, expressed as a percent of what we saw on June 1 when soil moisture was very high. In other words, values near 100% show a near full recovery while values less than 100% need more rain to recover.
I have created a new web page that contains the monthly precipitation totals during the 2011 drought, along with links to the 1980-2010 normals (where available). I will keep this page updated as we move into fall.
Link: The 2011 Drought in Illinois
Based on preliminary data, the first half of September in Illinois has been cooler and drier than average. The statewide average temperature was 67.6 degrees, 2.1 degrees below average. The statewide average precipitation was 1.26 inches, 0.26 inches below average or 83 percent of average.
The NWS Climate Prediction Center has released their outlooks for October and October-December. For Illinois there is an increased chance that temperatures will be above-average in both the October and October-December time frames. Also there is an increased chance that precipitation will be below-average in both October and October-December.
As posted earlier, this forecast is consistent with the known impacts of the rejuvenated La Niña event occurring in the Pacific Basin. La Niña tends to give us warmer and drier than average conditions in fall. Last fall was a classic example of this with temperatures 1.2 degrees above average and precipitation 12% below average.
The National Weather Service office in Davenport has issued this statement of a possible frost on Wednesday night:
Canadian high pressure will bring the threat of an early season frost by late Wednesday night. Areas along and north of Interstate 80 may dip down into the middle to lower 30s after midnight. These kind of temperatures will produce patchy to areas of frost by early Thursday morning. People in these areas should plan ahead and be ready to take the necessary precautions to prevent damage to cold sensitive vegetation. A Frost Advisory may eventually be issued for portions of the area. North winds maintaining 5 to 10 mph will help keep temperatures in the upper 30s south of I-80 and thus limit the frost potential in those areas.Normal 1st 32 degree temperatures range occur around early October in Northeast Iowa and Northwest Illinois, to mid October in West Central Illinois and Northeast Missouri.
According to the NOAA Climate Prediction Center press release, La Niña conditions returned in August and are expected to gradually strengthen and continue into this winter. This La Niña event first appeared last summer and continued in fall, winter, and early spring. By May, it had faded away. In fact, from May to July La Niña was not present in the Pacific according to the Climate Prediction Center. Only in August did it seem to return.
While La Niña events can continue for more than one year, it is very rare for one to disappear in spring and then reappeared in late summer. In fact, there are no other case like this in the historical records that go back to 1950, according to one of the primary indices used to measure La Niña and El Niño.
If La Niña continues to redevelop, the impacts on Illinois could include a fall that is warmer and drier than average and a wet winter all along the Ohio River Valley. The next set of seasonal outlooks from the Climate Prediction Center will consider the redeveloped La Niña. The new outlooks will be released on Thursday of this week.
La Niña is the name given to abnormally cold waters along the equator in the eastern Pacific Ocean. The changing weather patterns associated with La Niña effect not only the Pacific Basin but the U.S. as well. See the Climate Prediction Center link for more information current conditions and possible impacts.