Savage Thunder by Johanna Lindsey

Newly widowed after a shockingly brief marriage to an elderly British lord, Jocelyn Fleming still aches with the pain of unexplored desire. And now her restless heart is leading her far from the protective bosom of polite London society to the perilous beauty of the American West . . .and to Colt Thunder.

Breathlessly exciting but dangerously unpredictable, Colt is a loner whose Cheyenne blood burns hotter than the blistering Arizona sun. Jocelyn's wealth and title mean nothing to this strange whose passion rules his actions and his heart. But neither the wild desert stallion nor the untouched English rose can deny their irresistible attraction. . .or prevent the firestorm of emotion that erupts when their vastly different worlds collide.