If you choose to try on a river open to fishing, I suggest to check below a dam or a spillway where structure points break the stronger currents, and look for areas of slack water. In cold water, the fish use these slack areas to rest, and slack water may also be a few degrees warmer and may also hold baitfish. Bobber fishing using a live minnow for bait is a good way to set up in areas of slack current when water temperatures are cold.
On our inland lakes here in Kenosha County, I suggest to take the temperature of the water, as most fish are more active with water temperatures near 50 degrees. I also suggest to set up your baits like you will be fishing on the ice.
The fish will not chase bait or a lure very far when water temperatures are cold. The bobber combination will help slow up the action of your bait, and curious fish will be able to swim up to your bait with little effort and will not be turned off by the bait moving away. While this may sound complicated, this a very simple and productive way to attract fish in shallow water when the water temperatures are cold.
I also suggest to have a Plan B ready so you can make a move, especially if the bite is too slow or non-existent.
Back inside the Kenosha harbor at Lake Michigan, you will be looking for areas of clear water. The rainbow and brown trout are not as sensitive to water temperature as the coho or chinook salmon, which prefer water temperatures in the mid-50s.