The Windmaster can withstand winds up to 35-40 mph.  However, your umbrella is not warranted for wind damage.  Umbrellas should be closed and/or taken down when not in use or left unattended. There are variables to wind that cannot be replicated in testing.  In wind tunnel testing, all winds are straight and sustained; they do not simulate the uplifts found in the real world.  Securing your umbrella to a base is of utmost importance.