Illinois State Water Survey - University of Illinois at Urbana-Champaign

State Climatologist Office for Illinois

Long-Range Outlooks and Forecasting Techniques for Illinois

Dr. Jim Angel, State Climatologist

Official long-range forecasts, or outlooks, for the U.S. are issued by the Climate Prediction Center (CPC) of NOAA for the next month and for 3-month periods extending out to a year (see CPC). In addition, private consultants can provide tailor-made forecasts to users. See the American Meteorological Society for a list of consultants in your area.

The big breakthrough in the last 10 years has been the ability to predict El Niño and La Niña events ahead of time with some degree of skill. With this knowledge, impacts on the change in distribution of temperature and precipitation can be predicted. Unfortunately for us, most of the impacts of these events are mostly restricted to winter in Illinois and only for the stronger events (see impacts of El Niño/La Niña in Illinois).

Other statistical forecasting techniques include:

  • Using straight climatology - for example, planning on 11 days at or below zero in Chicago since that is the normal (see Illinois normals).
  • Using trends - for example, recent winters in Illinois have become milder (see Illinois trends), suggesting that next winter could be the same. Illinois State Water Survey research shows that an average of 5 to 11 years is best for predicting next year's temperature.
  • Using persistence - for example, warm January's lead to warm February's. This persistence or "memory" from one month to the next varies through the year and with the climate variable. See temperature and precipitation plots for more information. The relationships are not always strong or reliable but can serve as a guide in certain circumstances.

If you need help in finding and understanding long-range forecasts, please contact me (see main page under Contact).

Illinois State Water Survey

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Champaign, IL 61820-7463

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