From September through April, Phoenix enjoys mild weather and cultural events aplenty. Autumn is the choicest time to visit weather-wise, though the early months of spring have all the best festivals. Those hardy souls who brave a visit in summer can witness the mercury riding above 100°F (38°C) for weeks on end, commonly climbing well over 110°F (43°C) in midsummer. Summer is also monsoon season, when late afternoon thunderstorms blast the area and flash flooding becomes a concern for hikers. During the hottest spells, nobody does much of anything during daylight hours unless they're in an air-conditioned zone.