June in Wisconsin is a special time. The weather is fine and the "Monster" brown trout are a little more vulnerable. When brown trout get older they become nocturnal feeders. The bench mark for a big trout in this area is 20 inches and above.That hole that you have fished 50 times and not caught a single trout in the daytime is a prime area to try. Big trout are very territorial and will chase out any other trout in of their area.
This absolute monster slurped a hex emerger and stormed away like its tail was on fire.
When trout get really big they become carnivores and seldom eat insects. The exception to this rule is in June, when the environment is perfect, the big browns come out and put the feed bags on. Emerging mayflies are their targets. The bottom make up of a perfect mayfly species hexagenia limbata "hex"stream is silty and a little warmer than the average stream in the area.
The mayflies typically hatch at night. They emerge from their old bodies on the surface of the stream. They struggle and shake and fight on the surface to get rid of that old exoskeleton. They are very vulnerable at this time and the big brown trout come out and gorge themselves on these huge flies. It is typically really dark and the only way you can detect a bite is from the sound of the slurping or sucking sounds these leviathans make as they are dining on the biggest insect this area has to offer. You set on the slurp sound and hang on. Do NOT use an undersized fly rod for this night time attack. Have a stout new leader attached to that fly.
This nocturnal monster freight trained the mouse fly and immediately went in to an alligator roll trying to free itself.
You should also have an alternate attack plan in case that hatch doesn't happen. That stout rod you have rigged up can quickly be set up for another night time rig that is deadly. Big nocturnal browns 
big meals. I have personally seen a huge brown take a baby duck off the surface locally. There really are no baby duck flies available so the next best thing is a mouse fly.
Mice fall in to streams at night when they are out feeding themselves. The second they hit the water they are in panic mode. They try to get back to shore quickly. They usually motor non stop the direction they are pointing when they hit the water. This motion can be imitated my stripping your mouse constantly and quickly across the water. This stripping motion keeps the line tight and that is a good thing when that giant brown freight trains that mouse fly you need to set that hook immediately and you are going by feel in the complete darkness. A loose line means a lost fish of a lifetime.
Fishing at night can be very dangerous. You should scout your area during the daylight and make a plan of action with another angler. Do not try this alone. Please...I implore you...HANG ON TIGHT!
These flies are not to be used by the faint of heart .
