Hydrangea macrophylla 'Nikko Blue' is hardy in these areas:

Alameda, CA	Alamo, CA	Alsip, IL
American Canyon, CA	Angwin, CA	Antioch, CA
Baltimore, MD	Bayside, NY	Bronx, NY
Brooklyn, NY	Brownsville, TX	Canton, MI
Chicago, IL	Cicero, IL	College Point, NY
Conneaut, OH	Corona, NY	Danville, CA
Detroit, MI	Dorset, OH	East Claridon, OH
East Elmhurst, NY	Ecorse, MI	Elmhurst, NY
Elmwood Park, IL	Elyria, OH	Essex, CA
Evergreen Park, IL	Fawnskin, CA	Ferndale, MI
Florence, SC	Flushing, NY	Fontana, CA
Forest Falls, CA	Forest Hills, NY	Fort Eustis, VA
Fresh Meadows, NY	Glen Burnie, MD	Gwynn Oak, MD
Harper Woods, MI	Harrison Township, MI	Hunt Valley, MD
Jackson Heights, NY	Leasburg, NC	Lexington, NC
Liberty, NC	Linwood, NC	Little Neck, NY
Ludlow, CA	Macomb, MI	Marysville, MI
Maspeth, NY	Memphis, MI	Mercedes, TX
Middle Village, NY	Mission, TX	Modesto, CA
Moreno Valley, CA	Morgantown, WV	Mount Clemens, MI
New Baltimore, MI	New Haven, MI	New York, NY
Newport News, VA	North Ridgeville, OH	North Street, MI
Oakland Gardens, NY	Olmito, TX	Penitas, TX
Pharr, TX	Phelan, CA	Philadelphia, PA
Pikesville, MD	Pinon Hills, CA	Port Isabel, TX
Progreso, TX	Redlands, CA	Rego Park, NY
Rialto, CA	Ridgewood, NY	Rimforest, CA
Riverdale, IL	Saratoga, CA	Soquel, CA
Sparrows Point, MD	Staten Island, NY	Taylor, MI
Temperance, MI	Temple City, CA	Towson, MD
Trenton, MI	Tres Pinos, CA	Upland, CA
Virginia Beach, VA	Walnut, CA	Watsonville, CA
Wayne, MI	Westland, MI	Whitestone, NY
Whitmore Lake, MI