Carbondale, Illinois – Temperatures will climb into the upper 80s by Thursday afternoon, pushing near 90°F and bringing a summerlike stretch of heat across southern Illinois heading into the weekend.
According to the National Weather Service and NOAA’s Climate Prediction Center, southern Illinois is in an 80 to 90 percent probability zone for above-normal temperatures from April 16 through April 20. A strong heat dome over the Midwest and Ohio Valley will suppress rainfall and allow temperatures to steadily rise through the period.
In Carbondale and across Jackson, Williamson, and Franklin counties, highs are expected to reach 87 to 90°F between 2 p.m. and 6 p.m., with overnight lows holding in the mid to upper 60s. Along the I-57 and Route 13 corridors, dry air and persistent sunshine will rapidly dry vegetation, increasing wildfire risk in rural and wooded areas.
Marion and Mount Vernon will see similar conditions with highs in the upper 80s, while areas closer to the Mississippi River, including Chester, may briefly touch 90°F during peak heating. Despite the warmth, humidity levels will remain moderate, allowing fuels to dry quickly.
The precipitation outlook shows a 33 to 50 percent chance of below-normal rainfall early in this stretch. However, a transition begins late in the period as a storm track develops along and south of I-70, increasing the potential for heavy rainfall just beyond April 20, especially along the I-57 corridor.
Residents should avoid outdoor burning, stay hydrated, and limit strenuous activity during peak afternoon heat. Drivers should monitor vehicle temperatures and avoid parking on dry grass.
The most intense heat is expected April 18 through April 20, when a “much above normal” zone expands into southern Illinois. Additional advisories are possible as this pattern begins to shift toward a more active storm setup early next week.
