Wondering if I should wait for rainy days to pass before milling lumber.
I would think the higher humidity on these rainy days might cause boards I mill up to move a bit more after sitting overnight (if left in the shop) than if I waited and milled them on a drier day. When I mill up smaller pieces I just bring them in the house to sit until I use them. But that becomes a challenge with larger pieces so I wonder if I should just wait for the rain to pass.
My shop is an insulated garage.
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Humidity will definitely be higher on a rainy day, but the difference in humidity between a rainy day and a dry day in the same week probably isn't that significant compared to differences between summer and winter and natural outdoor vs conditioned indoor spaces.
I am assuming you are milling green lumber from logs, yes? But even if you're resawing kiln dried stock, the movement of moisture into and out of lumber is a slow process. I doubt you could document a big difference between milling on a rainy day and letting it sit for a while vs a milling on a dry day. That said, it is always a good idea to let rough lumber equilibrate under conditions close to those you would see in the finished product before you perform final dimensioning and planing.
Foreword, I do not believe in acclimating wood before using it if it’s been kiln dried. I use wood as it enters the shop or 30 years later and it behaves the same regardless. Waiting for a sunny dry day to work has never been something I did, more the opposite. Wood will change with seasons but not within days or even weeks, but the furniture you make will see those changes so it has to be built to tolerate those variations.
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I think it is more important to stop milling close to final dimension and check your wood is behaving.
Sometimes it will need another jointing before coming to final thickness.
I generally try to leave my wood for a couple of hours after initial milling to give it 'time to rest' but whether this is necessary or not is hard to say. I've seem cupping of up to 1mm develop in this sort of time frame, but it's rare to see movement after. Such is, I think, due to internal tension rather than moisture changes.
One exception though is thinner, wider stock - I find this can move so is definitely best milled as close to the time it will be used as possible.