Jim Angel, the Illinois State Climatologist, wrote yesterday that Chicago-area precipitation seems to have shifted around 1965:
First of all, northeast Illinois (Cook and several surrounding counties – see map below) has experienced a shift in precipitation over the last 120 years. This plot shows the amounts for each year as green dots, and an 11-year running average showing longer periods of dry conditions (brown) and wet conditions (green). There is a pretty remarkable shift from a drier climate between 1895 and 1965 with lots of brown, towards a wetter climate from 1966 to present where green dominates.
If you compare the average annual precipitation between the two periods, you get 836 mm for the earlier period and 935 mm for the later period. That is a 99 mm increase, or about 12 percent.
Of course, we have still experienced drought conditions in this later wet period, as noted in 2005 and 2012. However, the wetter years far outnumber the dry years since 1965. BTW, this pattern is not unique. I have seen this across the state.
So, with slightly warmer weather, milder winters, and more precipitation, it looks like Illinois might suffer less from climate change than other parts of the country. However, those conditions have led to increasing insect populations and more-frequent large precipitation events, with non-trivial costs.
At least we're not in South Florida, which not only faces complete inundation from rising sea levels, but also a climate-denying Congressional delegation.