The big question on my mind and the minds of IndyCar fans for the next month will be, "what will the weather be like in Indianapolis?" While specific details of what the weather may bring can't be pinned down until a few days in advance, we can look at several signals in the atmospheric pattern than can give a general idea about what may happen a few weeks in advance. For more details about long-term weather forecasting, please read this post. It is important to remember that long-term forecasts are a prediction of the chance of temperature or precipitation being above or below normal. We can't tell what the exact temperature will be, but we can tell if the general weather pattern will favor temperatures that are warmer or colder than normal, or precipitation above or below normal.
Based off the latest forecast from the Climate Prediction Center that was issued on April 29 (covering May 14 to May 27 - I realize the 500 is on May 29, but it's close enough to this forecast period that it wouldn't make much difference), the general weather pattern that is expected across the United States for the second half of the month is a trough across the western half of the country, with a ridge in the eastern half. If you're hoping for a warm and dry pattern for the later half of May in Indianapolis, this is good news.
There is a >60% chance that temperatures will be above normal in Indianapolis from May 14 to May 27. The normal high temperature in Indianapolis during this period is 72 to 76 degrees.
I'll have a detailed forecast for the Grand Prix of Indianapolis next Sunday, with forecasts for Indy 500 qualifying on May 15, and for the 100th Indy 500 on May 22.