Isle Royale Forums

How accurate is this chart from weathersparks.com. We are planning an August 2024 visit and I’m thinking it is telling me a 35° bag will be fine.

It's probably an average or extrapolation of mainland observations. But IR is sitting in the middle of a huge cold lake and the weather varies greatly, both day to day and depending on where you are on the island--you can have sunny 80s on the ridge and foggy 50s a couple miles away on the shore at the same time. Most experienced folks will take a 20 deg or warmer bag any time of the summer. I've seen upper 30s on the shore at night with the wind blowing off the lake in July. I used to take a 35 deg bag with a silk liner and was OK, but had some less than comfy nights with my base layer on as well. My newer 20 deg bag that I take now is more comfortable. So you're probably OK with the 35 deg bag, but could regret it, so I'd bring a warmer one if you have the option.

I usually bring a 30 degree quilt no matter the time of year (and 0 degree in spring). But that's because I know I'm a very cold sleeper. You know yourself best, and whether a 35 degree bag will be enough for you in the situations Ingo described.

I usually bring a lighter quilt and heavier liner. Then i plan on wearing base layers or more, as needed. In the spring, I will bring a warmer bag because i have been there for many nights below freezing. I agree with dcclark that this is very dependent on the individual,