Knowing how much heat these hand warmers produce, I do not see how they could hurt a club. You did not say which part of the club you put them against. I can not see an advantage to doing that. My golf balls stay pretty warm in my pockets without the hand warmers. When it is that cold (20*) I stay inside, because the superintendent will not allow us on the greens.

I could be wrong as I am not sure how a hand warmer could damage the club itself. My evidence is this, I live in Texas, and my clubs are usually in either my back seat or my covered bed in my truck. The Texas summers get well over 100 degrees and I cant say i have seen any damage or anything to my current Scotty. Not sure what kind of hand warmer you are using but i doubt it gets any hotter then the Texas summers. Just my thoughts.

Ted,
It's no more harmful than pouring 135 deg F hot water over your putter. I would not worry about this. Stay warm and have fun.

don't think that this temerature switch can create problems to your putter... in summer it surely get ways hotter

I don't see how that little heat could damage your putter. What I wonder is why you are play golf at 20 degrees! Heck that is cold! The greens would be frozen and they don't let us play when they are frozen.

Wow 20 degrees! I don't think the heat of the hand warmers would damage your putter. They won't let us on the greens or course here in NC if its freezing and frost on the ground. However we can play here at least 80% of the winter.

Have fun out there⛳️⛄️