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