Went in on May 16 a few years ago through Beaverhouse. Ice had only been off a few days and found small snow patches in the flooded portages and big ice chunks along the shoreline. We were cold all week and resorted to laying on the rocks to get some comfort and relief when the sun did finally shine. I was glad to have a warm sleeping bag, winter coat and knit hat along, which I ended up sleeping in every night night. Saw sputtering snowflakes one day, rain, wind, some sun and warming temps on the last day of our trip. We saw some amazingly large pike in the shallow but only got the a tiny one to bite, it was 38". Fishing was a little slower than we hoped for, but we caught some big SM and a few bigger LT and only enough W for dinner. We managed to eat all of our food before the end of the trip, probably due to the cold, and our last dinner was only fish (N, SM, W) and some dried fruit. With my limited experience I much prefer Sept. over May.

Have been into Q three times in your timeframe, once late May (Memorial Day) and twice in September (Labor Day). Luckily had very good weather each time. Water temps key in where to find and how to fish. We had great SB topwater action in late May, jigs and cranks in September. The water was still cold in May and still warm in early September. Not many people in the park on any of the trips which used Stanton, Nym, and Beaverhouse entry/exits. Walleye fishing was more consistent in September, seemed like fish were much more concentrated once found. Any time you can get in the park is the best time to go but as several previous posts said, be prepared.