No, you don’t.. unless you live in an area where it does often rain..

But not having any protection from the weather, does slow you down (particularly in summer if you live in QLD), and you need to change the way you would normally work to accommodate those weather changes and sometime, it can stop your project all together..

I do recommend some form of tarp or a gazebo (at least big enough for the working table area) as it does make things a lot easier and it can actually save you money in the long run as the project will be completed earlier..