A cool down is coming in the middle of October.

Temperatures could be slightly below normal during the middle of October. The target dates would be between October 12 - 19. Say good bye to the 80's and maybe even the high 70's after this period.

From the NWS:

.LONG TERM /Friday through Monday/...
Issued at 340 AM EDT Tue Oct 3 2017

An active and unsettled weather pattern will continue through much
of the extended as the cold front remains draped across the region
into early next week.

The convective threat will be primarily focused over northern
portions of the forecast area on Friday and Friday night in closer
proximity to the boundary. Decent extended model agreement exists
on a sharp upper wave ejecting out of the northern Plains on
Friday and tracking into the Great Lakes Saturday while steadily
strengthening. The upper wave will help to generate a surface low
along the boundary which will rapidly intensify on Saturday as it
cuts across the Great Lakes. A trailing cold front will be drawn
through central Indiana Saturday afternoon and evening as a result
with the potential for stronger convection to accompany the
boundary.

Model consensus favoring the deepening low pressure lifting
north-northeast towards James Bay rapidly Saturday night with the
frontal boundary getting left behind over the Ohio Valley.
Confidence lowers from this point forward as several factors could
contribute to additional rain and convection impacting the region
into early next week. Some model agreement starting to show
regarding tropical development over the Gulf of Mexico this
weekend. The system is expected to lift north near or just east of
the Mississippi River by late Sunday and eventually get drawn
into the Tennessee and possibly Ohio Valleys by Monday as it
interacts with yet another wave kicking east into the region. The
remnant boundary could serve as a focus for additional showers and
thunderstorms with higher pops once again warranted for Sunday
night and Monday. The front will sweep the low lifting out of the
Gulf off to the east by early Tuesday.

Temperatures will remain largely above normal through the weekend
with highs ranging from the mid 70s to lower 80s. The departure of
the front just outside the 7 day will enable a strong Canadian
high pressure to expand across the Midwest. Trends support much
cooler weather across central Indiana by the middle of next week.