Good Morning, 

Thanks for your question. 

Please click on the following link all about growing raspberries in MN: https://extension.umn.edu/gardening-minnesota/growing-raspberries-home-garden

If you scroll down, there are sections about diseases. 

This information states: 

Heat damage

Hot days with strong sunlight may cause sunscald on berries forming white or colorless drupelets (the small, individual, seed-containing parts of each berry). The white drupelets will be flavorless, but there is no harm in eating them.

Once the weather cools, plants will produce normal berries. Heat can also cause berries to ripen faster than you can pick them, which can attract insects. Pick ripe fruit immediately.

With the hot and humid weather we've been having, I believe this is the issue. 

I am assuming you have had the same hot weather up there in St. Louis county as we've had in the southern half of the state. 

Good Luck!