Outlook for Summer, Fall in Illinois

The National Weather Service released their latest outlooks for this summer and fall today. Looks like a warmer summer and fall may be in store for Illinois.

Transition from El Niño to La Niña

Most models predict the end of El Niño and a brief period of ENSO-neutral by early summer. La Niña is favored to develop during the summer, with about a 75% chance of La Niña during the fall and winter 2016-17. La Niña occurs when colder-than-average waters appears in the eastern Pacific Ocean. It is the opposite phase of El Niño although the effects on the US are not as strong or as clearcut as an El Niño event. I will post more on La Niña soon.


Here are the outlooks for June. Click on the maps to enlarge. Most of Illinois, except for the far north, has an increased chance of being wetter than normal (green). Meanwhile, the eastern third of Illinois has an increased chance of being warmer than normal (red). Areas not shaded and marked EC indicated areas where there are no strong evidence of conditions being too cool, too dry, too wet, or too dry as the case may be. EC stands for Equal Chances of above, below, and near-normal conditions.  EC is not a bad place to be.


For the summer months of June, July, and August, the outlook for Illinois is EC for rainfall and an increased chance of being above-normal on temperatures. It is a rare combination in Illinois to have a warmer than normal summer without being drier than normal as well. An examination of the 40 warmest summers in Illinois revealed that 21 had below-normal rainfall as well. Only 13 had near-normal rainfall (as implied in the forecast here), and 6 had above-normal rainfall.

September – November

For September, October, November, southern Illinois has an increased chance of being drier than normal. This is part of a larger area of drier conditions in the South and Southwest. The rest of Illinois is EC. All of Illinois, and almost all of the US has an increased chance of being warmer than normal in the fall.

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