Apr 11 | Climate Review and Weather Forecast

We had a bit of a calmer weather week as we settled into April. Average temperatures this week ranged from the high 30s to the mid-50s, between 2 and 5 degrees below normal. April to date has been 1 to 4 degrees cooler than normal as well, following a top 10 warmest March on record statewide. In fact, last month was the warmest March in Illinois since 2012.

We’ve gotten a better picture of the precipitation and flooding across southern Illinois from last week’s storms. 4-day precipitation totals ranged from around 2 inches in parts of central Illinois to over 10 inches in far southern Illinois. Most of the state south of Interstate 64 picked up at least 6 inches of rain through Sunday. The heavy rain caused many rivers to reach above flood stage, and caused some significant flash flooding, including in Salem. Most of the smaller streams have already reached peak streamflow, while the bigger rivers will likely peak sometime this weekend and into early next week. This includes the Ohio River, which is expected to reach its highest peak at Old Shawneetown since 2011. The Mississippi River at Memphis will have likely risen by over 30 feet in just a week and a half as the water drains towards the Gulf of Mexico. In fact, a back of the envelope calculation suggests that just the entire Ohio River Basin picked up roughly 56 million acre feet of water in just four days last week. To put that in perspective, that’s about twice the amount of water stored in the entire Colorado River Basin right now… Lake Powell, Lake Mean, all of it.

Looking ahead, our drier streak is likely going to continue next week, with precipitation totals forecasted mainly less than a quarter of an inch across the state. Temperatures will be much closer, if not slightly above, normal next week, with highs in the 60s and lows in the 40s statewide. More persistent mild weather should help sustain soil temperatures that are more conducive to proper germination as planters will likely be spotted in places that haven’t been flooded out. The week two outlook, taking us into the final week of April, shows best chances of warmer than normal conditions statewide, and drier than normal weather in southern Illinois. This will be key to helping that region dry out after last week’s storms.