The NWS Climate Prediction Center released their updated outlook for June, 2015. The new June outlook shows northern Illinois, including the Chicago area, with an increased chance of warmer and drier than average conditions.
Much of central and southern Illinois has equal chances (EC) of above, below, and near-average temperature and precipitation. This is different from the previous outlook for June that was released mid-May. That one had central and southern Illinois with an increased chance of wetter than average conditions.
While these outlooks cover the entire month, most of the model forecast skill is in the first 10 days. So the features of warmer and drier conditions in northern Illinois may be more in line with what’s expected in the first week or two and less with the entire month. More useful information can be obtained from the NWS 6-10 and 8-14 day forecasts which are updated daily.
Here is a quick update on the statewide monthly temperature and precipitation departures from average for 2015 in Illinois.
February 2015 stands out as a painful reminder of how cold it was late in the winter. However, both April and May have been warmer than average. All together, the average temperature of the first five months of 2015 stands at 40.5 degrees, 2.3 degrees below average.
Despite cool weather at times, May was 2.3 degrees above average on temperature and one inch above average on rainfall with 5.6 inches.
The statewide average rainfall was 5.6 inches, which was 1 inch above average and the 22nd wettest May on record. Some of the heaviest amounts were seen in northwest Illinois and just southeast of St. Louis (orange and red areas on the map). The highest reported monthly rainfall total was 9.41 inches at Red Bud (Randolph County). The next highest total was 8.77 inches at Mt. Carroll.