Summer-like temperatures prevailed across central and southeast Illinois for much of the first half of April. Temperatures averaged 10-15 degrees above normal through April 15th with several days seeing highs in the 80s and lows in the 50s. These readings were more typical of mid to late June! Normal highs for early April are in the upper 50s and lower 60s, while lows are typically in the upper 30s and lower 40s.
The reasons for the extended period of warm air residing over the Midwest are complex but basically result from a "blocked" weather pattern which allowed high pressure at the surface and aloft to set up across the nation's mid-section. Several days of southerly to southwesterly winds allowed warm air to move into the region, and plenty of sunshine acting on relatively dry air produced further warming of the airmass.
While it was very warm, few individual daily records were established. A record high was tied in Springfield on April 6th at 85 degrees. The most unusual aspect of this warm stretch is its duration. Many locations in central and southeast Illinois were more than 10 degrees above normal for 12 of the first 15 days in April, while several days were more than 20 degrees above normal. For detailed climate information check out our Local Climate webpage.
The map below shows the large area of above normal temperatures across the Midwest for April 1-14, courtesy of NOAA MRCC. Note the area of highest above normal readings (bright red shading) across central Illinois and Indiana.
The graphs below show daily high and low temperatures for several locations in central and southeast Illinois for April 1-15. A detailed description of how to interpret the data is located below each graph. Note the number of days that approached record highs for each site.