i have a freestanding 8-3 sign 200lb i need to know how to install it so it will with stand 100mile winds?

Question

i need to know pole size or i beam size and how big to make my footing

Answer 1

I do not have data for wind loading at 100mph but at 75mph the pressure will be over 14#/sf.

The total pressure of a 75mph on the 8x3 ft sign will be (14#/sf)24sf=336#
This is at only at 75 mph. at 100 I would estimate about 1000#

So build strong or it will fly. Placing holes in the sign can reduce its effective area. Use fabric to make a sign if it gets airborne it will provide little if no damage.