There is no need to underclock, unless the temperature in your garden thread gets above 50-60 degrees Celsius. I'm not sure whether you can underclock it dynamically, but there's probably something to do it.

In the garden shed heat should not be a problem but if the air is humid enough for water to accumulate on it that is a bad thing.

I'd say just put it in a case to deal with the dampness unless water would condense on it.

There is no need to underclock, unless the temperature in your garden thread gets above 50-60 degrees Celsius. I'm not sure whether you can underclock it dynamically, but there's probably something to do it.

In the garden shed heat should not be a problem. However if the air is humid enough for water to accumulate on it then you may run into some large problems.

I'd say just put it in a case to deal with the dampness unless water would condense on it.