The forecasts for August and the three-month period of August-October show most of Illinois with an increased chance of being cooler and wetter than average.
A significant El Niño event has developed in the Pacific Ocean and has a 90% chance of remaining throughout 2015 and an 80% chance of remaining until next spring. This is expected to have significant impacts on the weather in the US.
El Niño events occur when the waters in the eastern Pacific along the equator are warmer than usual. This changes the weather patterns over the Pacific and US.