We had a thread some time back about big and tall sizes, but I'll be darned if I can find it!
I remember looking up some options at that time. A number of the big and tall stuff isn't big or tall enough (the poster was, I believe, close to your size). You really have to check the vendor's size charts! I do remember that LL Bean carries rain gear that appears to be big enough.
I'd suggest searching for tall/big sizes in rain jackets and rain pants, and checking each vendor's size charts. First, though, check your measurements (chest, sleeve length, jacket length, waist, hips, trouser length), and compare them to the size charts. Do remember that you need room inside the rain gear for your insulating clothing!
Unfortunately, I doubt that big/tall sizes and light weight go together, especially since your choices in those sizes will be limited.
Edited by OregonMouse (06/12/18 03:24 PM)
Edit Reason: add comment on weight
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey