The USDA has just released their new Plant Hardiness Zone Map. This is a much-needed update using the 30-year period of 1976-2005 versus the old USDA map which used the period 1974-1986.
One of the outstanding features of the new map is the northward shift of the hardiness zones in Illinois. For example, the boundary between zones 5 and 6 have shifted about 60 miles to the north. Zone 4 has left Illinois in the new map. In addition, the new map shows a lot more detail including the warming effect of the Chicago urban area (see map below).
In the second figure, the minimum winter temperature for each year is shown for Champaign-Urbana. The old USDA plant hardiness zone map used an unusually short period during one of the colder periods in the record (1974-1986). The general trend in the data shows an increase in the minimum winter temperature from the late 1800s to about 1950, followed by a cooling trend to the 1980s, and finishing with a warming trend through 2005. Interestingly, the last few years showed a cooling trend – except for this year when our coldest temperature so far is 4°F.
The other important feature in the second figure is that even if an area changes Zones, there is still a lot of year to year variability in the minimum temperature for winter. For example, while Champaign-Urbana is nearly classified as Zone 6 in the new map, Champaign-Urbana dipped into Zone 4 a few times (-20°F or less) in the last 30 years. In fact, as a gardener I would say that the period from the 1930s to the early 1970s was more benign and less challenging than the 1980s and 1990s with respect to winter temperatures. Summer conditions would be another story since the 1930s and 1950s were marred by severe droughts.
Severe Weather in January
It was somewhat strange seeing lightning and hearing thunder yesterday evening, considering that it was January. The NOAA Storm Prediction Center listed two reports of 1 to 1.5 inch hail around Mt. Vernon. There were other reports of high winds and wind damage such as trees down. Meanwhile, tornadoes were reported in Arkansas, Tennessee, Mississippi, and Alabama. You can see the preliminary report at http://www.spc.noaa.gov/climo/reports/120122_rpts.html
While tornadoes are rare in Illinois in January and the other winter months, they do occur. Here are the number of tornadoes by month for Illinois (first figure) and their distribution around the state (second figure). You can see more figures like these here and here.
And here is their distribution across the state for January:
Getting Around Illinois in Winter
The Illinois Department of Transportation maintains a website called http://www.gettingaroundillinois.com/ According to the site,
Getting Around Illinois is a web-based interactive mapping site that provides the ability to search and display several sources of transportation data. You can find information on winter road conditions, average annual daily traffic, road construction, trucking routes, and planned road projects.
From that main page, you can get current winter road conditions at http://wrc.gettingaroundillinois.com/pages/wrc.htm. I have found this site to be very valuable for making travel plans during or after a winter storm in Illinois.
Have you ever noticed the weather instruments alongside Interstate Highways? Those systems are called Road Weather Information Systems, or RWIS for short. They include weather sensors as well as roadway sensors to measure pavement temperatures and detect wet or icy conditions. Here is the link for the RWIS data in Illinois: http://www.gettingaroundillinois.com/mapviewer.aspx?mt=rwis
Illinois Site Close to State Record
The statewide average precipitation for 2011 in Illinois was 45.62 inches, 5.43 inches above normal, making it the 10th wettest year on record. The largest precipitation totals for the year came from southern Illinois. In fact, one site – Du Quoin – came close to reaching the statewide record of 74.58 inches set at New Burnside in 1950.
Here are the outstanding annual precipitation totals for 2011:
- 72.11 inches at Du Quoin
- 70.77 inches at Cairo
- 70.58 inches at Grand Chain Dam
- 69.97 inches at Carbondale
- 69.16 inches at Murphysboro
- 66.89 inches at Olney
- 66.41 inches at Grayville
- 66.18 inches at Brookport Dam
- 64.50 inches at Mt. Vernon
- 63.98 inches at Shawneetown
However, not everyone was so wet in 2011. A few sites in central and western Illinois reported 30 inches or less. These include Lake Springfield with 25.34 inches, Illinois City Dam #16 with 27.47 inches. One of the driest major cities was Springfield with 30.61 inches, reported at the airport.
We are waiting for final reports from several sites. As a result, there could be more locations added to the wettest and driest spots in Illinois in 2011.