From Real Goods, who’ve been doing the sustainability thing for almost 30 years:
We generally advise that a good year-round wind turbine site isn’t a place that you’d want to live. It takes average wind speeds of 8 to 9 mph [3.6-4 m/s, or 12.9-14.5 km/h] and up, to make a really good site. That’s honestly more wind than most folks are comfortable living with.
— Solar Living Sourcebook, 12th ed., p.80