It has all 4 seasons. Summers are hot, humid, and rainy. Winters are pretty mild, but with a little snow. Weather can be pretty variable, changing day-to-day, so clothing that can be layered is helpful.
Southern Indiana is covered in this mission as well.

There are chiggers and ticks in the summer, so if you go into a wooded or tall grass area, you need to check for ticks as soon as possible. Consider buying a cheap tick remover.