Re: S.E. Minnesota
Localized thunderstorms like the ones we saw last week can drop variable amounts of water from valley to valley. One valley might get 8". The next valley might get 1.5". Some thin water can clear a 3-4" rainfall in 24 hours, but since most of the streams originate from farm land, most will clear much slower. So, some streams in the region may be blown out, but I have yet to experience a storm that blew out the entire region.
I know my advice is a bit late for your planned trip, but hopefully it'll help for the future. Be prepared to scout many streams. Go up to the thinner sections of the streams, too. As a rule of thumb, streams that feed from state parks or state forest land will clear faster than streams that feed from farm land. SE Minnesota covers a lot of area. If you're willing to drive around and scout a bunch, you can always find fishable water. Try to travel perpendicular to the path of the storms. If the storm came over NW->SE, and the stream I wanted to fish was blown out, I'd head NE or SW to try to find fishable water.
And, if you can't find clear water, don't despair. Driftless trout will still hit streamers, especially leech patterns, in murky water.