Got a source for that? This says "typically between 45 and 80 mph, most wind turbines cease power generation and shut down." That may be more relevant to residential (tiny) wind turbines. But, 30 MPH? I'm going to say no way that's the case on modern wind farms.
(Help me out here, DungeonMaster. You're the windpower wonk.)
Easiest way is see for yourself on any of the commercial web sites that sell wind turbines and read the fine print on the models.
It’s possible brand new designs would handle faster winds. The very high wind speeds thrown around are what they can tolerate without damage, not where they can produce electricity.
Cut out speed for windturbines is usually pretty close to 50 mph. Full load power is usually around 30mph but lately that is dropping due to the larger rotors/mw of newer turbines.