Arizona is a year-round destination, although people head to different parts of the state at different times of the year. In Phoenix, Tucson, and other parts of the desert, the high season runs from October to mid-May, with the highest hotel rates from January to April. At the Grand Canyon, summer is the busy season.
The all-around best times to visit are spring and autumn, when temperatures are cool in the mountains and warm in the desert, but without extremes (although you shouldn't be surprised to get a bit of snow as late as Memorial Day in the mountains and thunderstorms in the desert Aug-Sept). Late spring and early autumn (specifically May and Sept) are also good times to save money -- low summer rates are still in effect at the desert resorts -- and to see the Grand Canyon when it's not its most crowded. In spring, you might also catch great wildflower displays, which begin in March and last until May, when the tops of saguaro cacti are covered with waxy white blooms.
If for some reason you happen to be visiting the desert in July or August, be prepared for sudden thunderstorms. These storms often cause flash floods that make many roads briefly impassable. Signs warning motorists not to enter low areas when flooded should be taken very seriously.
Also, don't even think about venturing into narrow slot canyons, such as Antelope Canyon near Page or the West Fork of Oak Creek Canyon, if there's any chance of a storm anywhere in the region. Rain falling miles away can send flash floods roaring down narrow canyons with no warning. In 1997, several hikers died when they were caught in a flash flood in Antelope Canyon, and in 2009, a flash flood inundated the parking lot at Sedona's Tlaquepaque shopping center.
One more thing to keep in mind: Sedona is just high enough that it actually gets cold in the winter -- sometimes it even snows. So if you're looking for sunshine and time by the pool, book your Sedona vacation for a time other than the winter.
The first thing you should know is that the desert can be cold as well as hot. Although winter is the prime tourist season in Phoenix and Tucson, night temperatures can be below freezing and days can sometimes be too cold for sunning or swimming. However, although there can be several days in a row of cool, cloudy, and even rainy weather in January and February, on the whole, winters in Arizona are positively delightful.
In the winter, sun seekers flock to the deserts, where temperatures average in the high 60s (low 20s Celsius) by day. In the summer, when desert temperatures top 110°F (43°C), the mountains of eastern and northern Arizona are pleasantly warm, with daytime averages in the low 80s (high 20s Celsius). Yuma is one of the desert communities where winter temperatures are the highest in the state, while Prescott and Sierra Vista, in the 4,000- to 6,000-foot elevation range, claim temperate climates that are just about ideal.
Banks, government offices, post offices, and many stores, restaurants, and museums are closed on the following legal national holidays: January 1 (New Year's Day), the third Monday in January (Martin Luther King, Jr., Day), the third Monday in February (Presidents' Day), the last Monday in May (Memorial Day), July 4 (Independence Day), the first Monday in September (Labor Day), the second Monday in October (Columbus Day), November 11 (Veterans' Day/Armistice Day), the fourth Thursday in November (Thanksgiving Day), and December 25 (Christmas). The Tuesday after the first Monday in November is Election Day, a federal government holiday in presidential-election years (held every 4 years, and next in 2012).
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.