Even though Arizona is known for warm, sunny winters, frost is surprisingly common in December and January — especially in areas like Fountain Hills, Rio Verde, and northeast Scottsdale that sit at slightly higher elevations. Even lower-elevation areas such as Scottsdale, Paradise Valley, and North Phoenix can experience frost on clear, calm nights when cold air settles in open desert spaces. A single cold night can burn leaves, damage young trees, or kill tender plants entir