Hopefully you haven't gotten used to highs in the 70s and little in the way of humidity. Summer-like heat and Florida-like humidity are returning to Michiana by this weekend. They'll likely hang around for at least the first three days of next week as well. While we won't be breaking any records in the temperature department with highs in the upper 80s, it will certainly be a good reminder that summer doesn't end for another month.
Sunday, Monday and Tuesday will likely be the hottest days with highs in the 85°-92° range each afternoon. When you factor in extreme humidity in the form of dew points around 75°, it will "feel like" the 90s each day. Some locations could see maximum heat index temperatures reach or eclipse 100°, especially on Sunday. Put simply, you won't want to be outside unless you're in a pool or lake.
A few isolated showers or thunderstorms are possible across Michiana Saturday thru Monday, but washouts are NOT expected.
Sunday thru Tuesday will likely wind up being the hottest 3-day stretch since July 3-5. We could also see our first 90-degree high temperature in South Bend since August 4th and 5th. Beyond Tuesday, models disagree quite a bit. That's why there is significant uncertainty in terms of if the heat and humidity will last into the second half of the week. It's possible, but the forecast beyond Tuesday could swing in either direction.