When does paper birch bark pop

[Sauna freak]

In Northern MN.  I was thinking May or June, but now I'm second guessing my memory. I cut a big pile of it one year, and as it dried the bark sections popped right off giving me a few years worth of fire tinder. I know the birch I cut from fall through mid winter holds the bark tenaciously for a long time. Just can't remember for sure now if it was March and April or May and June. 

[beenthere]

May be a bit earlier than May, but most likely when the Birch buds begin to swell and the maple sap collectors are active in your area. Depends on the weather.

[brewdog]

when maple stop runing.