If your bay window is on the second floor then you should install all of the vinyl on the first floor without any problems.
How to install lp siding on a bay window.
Expert advice on how to install wood or fiber cement lap siding including how to prepare exterior walls and lay out siding for installation.
Remove the pieces of vinyl siding from around the window area.
This is much like building a frame around the windows so be sure to account for the width of the trim when measuring to cut these pieces.
Some other bay windows have flanges.
Step 2 prepare the window.
Lap siding also called horizontal siding or clapboard may be made of wood fiber cement plywood hardboard or similar materials.
Engineered wood siding typically butts into the trim pieces so it is necessary to start by installing the trim at the windows and doors.
With such units you ll need to set the window in temporarily shim it square mark for cutting the siding to accommodate the casing and cut the siding.
Use a siding removal tool.
Use this tool by inserting it where a piece of vinyl overlaps a piece below it and then sliding it across until you reach the end of the piece.
Do not cut the vinyl off.
On the approach to the bay window keep the vinyl siding as flat as possible and secure it at regular intervals so that it is defended against wind traveling under the siding.