Question for those in the know...and to frame it, I want to use this info to help the rest of my group prepare properly & safely (ditch kits, etc) for a trip on water that was recently solid.

What water temps would you expect in typical BWCA lakes around May 13-18? Sounds like ice is either out or about to be out across the BW...

Probably 45-50F depending on the week leading up to your trip. Water around Knife/Kekekabic (big, deep lakes) was around 50-55F during the first week of June last year. Mid-May water temps are definitely enough to cause hypothermia with ease. Bring some of those fold up space blankets, practice warm water bottles in crotch and armpits (high circulation areas), etc. And always, always wear a PFD. Even if it's dead calm. The water is cold enough to moderately paralyze you. Just wading into a shallow bay (warmer water) to wash some dirt off, on like June 5th, I was taking gasping breaths and had to acclimate for a few minutes before dunking myself a few times and promptly getting the heck out of the water. I also waded into a bay on Ensign to retrieve a lure I could see and I was also taking gasping breaths (involuntarily). It was quite cold then, so I imagine it's going to be even colder 2 weeks earlier. Just be prepared.

I used to do a lot of whitewater kayaking / canoeing, often as early as March. Even with wetsuits on that moment you are immersed in extremely cold water creates a moment of shock. Kayaking we would have the Eskimo down to where it was an automatic response. It would still be disorienting. For early cold water bwca type trips a wetsuit is not practical. If there was concern regarding going in the water we would wear our rain jackets and pants, these layers are helpful in holding in a bit of body heat. Always a pfd in recently thawed lakes.

Thanks for the data point!

Indeed, PFDs are never optional. Ability to rapidly make fire and an emer blanket in the vest...

If you are on big water in iffy conditions if is a good practice to lash your packs in the canoe. If they are secured properly they will displace water and add buoyancy to a swamped canoe. Done correctly it is possible to get out of the water and into your canoe and paddle, you are no longer immersed. Unless the situation is desperate stay with the canoe.

Cold water will cause your canoe to transfer the cold temps through your canoe to your feet. You might consider some layered cardboard to slow the process. Your feet will thank you later.

I seem to recall taking a near surface temp of 47 last year on Knife during the third week of May, and a few degrees colder 5 feet down. Ice had gone out about 10 days before, but we had a string of warm sunny days. Cold enough to cause the gasp reflex and quick loss of motor skills, which is a much bigger worry than hypothermia. I can be a bit cavalier about tipping in the warm summer months, but I take the cold water of May very seriously.

I recommend you dress warm, dry foot, paddle near shore, be confident in your ability to swim or paddle your capsized canoe to shore, and properly waterproof and secure your extra clothing and important equipment.

I have swam to shore and changed into dry clothing in the snow with no issues.