Packing for a trip to Phoenix won't stretch your closet. While summers can be outrageously hot, beautiful temperatures prevail the rest of the year, and the city's casual attitude make jeans and T-shirts acceptable for all but the finest of restaurants. If you're visiting in summer, shorts are a must. In winter, light jackets can be necessary at night. Year-round, bring sunscreen, a swimsuit and hat — while the weather may cool down, the sun shines 300 days a year. Outdoor activities abound in the Valley, so be sure to bring good walking shoes. A cardigans or light jacket is another must for Phoenix year-round, with restaurants and malls blasting the air-conditioning day and night.